is continuous at x = 0, then find the values of a and b. from M
Advertisement

If space space straight f open parentheses straight x close parentheses equals open curly brackets table attributes columnalign left end attributes row cell fraction numerator sin open parentheses straight a plus 1 close parentheses plus 2 sinx over denominator straight x end fraction comma space straight x less than 0 end cell row cell 2 space space space space space space space space space space space space space space space space space space space space space space comma space x equals 0 end cell row cell fraction numerator square root of 1 plus b x end root minus 1 over denominator straight x end fraction space space space space space space comma space straight x greater than 0 end cell end table close
is continuous at x = 0, then find the values of a and b.


Given space that space straight f space is space continous space at space straight x space equals space 0

If space space straight f open parentheses straight x close parentheses equals open curly brackets table attributes columnalign left end attributes row cell fraction numerator sin open parentheses straight a plus 1 close parentheses plus 2 sinx over denominator straight x end fraction comma space straight x space less than space 0 end cell row cell 2 space space space space space space space space space space space space space space space space space space space space space space comma space x equals 0 end cell row cell fraction numerator square root of 1 plus b x end root minus 1 over denominator straight x end fraction space space space space space space comma space straight x space greater than space 0 end cell end table close

Since space straight f left parenthesis straight x right parenthesis space is space continous space at space straight x equals 0 comma space limit as straight x rightwards arrow 0 of straight f space left parenthesis straight x right parenthesis space equals limit as straight x rightwards arrow 0 of straight f space left parenthesis 0 right parenthesis
Thus space straight R. straight H. straight L space equals space limit as straight x rightwards arrow 0 of straight f space left parenthesis straight x right parenthesis

space equals space limit as straight x rightwards arrow 0 of straight f space left parenthesis 0 plus straight h right parenthesis

equals space limit as straight h rightwards arrow 0 of space space fraction numerator square root of 1 plus bh end root minus 1 over denominator straight h end fraction

equals limit as straight h rightwards arrow 0 of space fraction numerator square root of 1 plus bh end root minus 1 over denominator straight h end fraction space straight x space fraction numerator square root of 1 plus bh end root plus 1 over denominator square root of 1 plus bh end root plus 1 end fraction

equals space limit as straight h rightwards arrow 0 of space fraction numerator 1 plus bh minus 1 over denominator straight h left parenthesis square root of 1 plus bh end root plus 1 right parenthesis end fraction

equals space limit as straight h rightwards arrow 0 of space fraction numerator straight b over denominator square root of 1 plus bh end root plus 1 end fraction

equals straight b over 2

Given space that space straight f space left parenthesis straight x right parenthesis space equals space 2

rightwards double arrow space limit as straight x rightwards arrow 0 of straight f space left parenthesis straight x right parenthesis space space equals space straight f left parenthesis 0 right parenthesis

rightwards double arrow space straight b over 2 space space equals space 2 space

rightwards double arrow space straight b equals space 4

Similarly comma space

straight L. straight H. straight L space equals space limit as straight x rightwards arrow 0 of straight f space left parenthesis straight x right parenthesis

space equals space limit as straight x rightwards arrow 0 of straight f space left parenthesis 0 minus straight h right parenthesis

equals space limit as straight h rightwards arrow 0 of fraction numerator sin space left parenthesis straight a plus 1 right parenthesis left parenthesis 0 minus straight h right parenthesis plus 2 sin left parenthesis 0 minus straight h right parenthesis over denominator 0 minus straight h end fraction

equals space limit as straight h rightwards arrow 0 of fraction numerator negative sin left parenthesis straight a plus 1 right parenthesis straight h minus 2 space sin space straight h over denominator negative straight h end fraction

equals space limit as straight h rightwards arrow 0 of fraction numerator negative sin space left parenthesis straight a plus 1 right parenthesis straight h over denominator negative straight h end fraction space plus space limit as straight h rightwards arrow 0 of fraction numerator negative 2 sin space straight h over denominator negative straight h end fraction

equals space limit as straight h rightwards arrow 0 of fraction numerator sin left parenthesis straight a plus 1 right parenthesis straight h over denominator straight h end fraction fraction numerator left parenthesis straight a plus 1 right parenthesis over denominator left parenthesis straight a plus 1 right parenthesis end fraction space plus space 2 stack space lim with straight h rightwards arrow 0 below fraction numerator sin space straight h over denominator straight h end fraction

equals space straight a plus 1 plus 2 space space space space space space open square brackets therefore space lim space fraction numerator sin space straight theta over denominator straight theta end fraction equals 1 space close square brackets

Given space that space straight f space left parenthesis straight x right parenthesis equals 2

rightwards double arrow stack space lim with straight x space rightwards arrow 0 below space straight f space left parenthesis straight x right parenthesis space equals space straight f space left parenthesis 0 right parenthesis
rightwards double arrow space straight a plus 1 plus space 2 space space equals space 2
rightwards double arrow space straight a space equals negative 1
1266 Views

Advertisement
if space cos space left parenthesis straight a plus straight y right parenthesis space equals space cos space straight y space then space prove space that space dy over dx space equals fraction numerator cos squared left parenthesis straight a plus straight y right parenthesis over denominator sin space straight a end fraction
Hence space show space that space sin space straight a space fraction numerator straight d squared straight y over denominator dx squared end fraction plus sin space 2 space left parenthesis straight a plus straight y right parenthesis dy over dx equals 0

Given space that comma

straight x space cos space left parenthesis straight a plus straight y right parenthesis space equals space cos space straight y space.... space left parenthesis straight i right parenthesis

rightwards double arrow space straight x space equals space fraction numerator cos space straight y over denominator cos space left parenthesis straight a space plus space straight y right parenthesis end fraction space... space left parenthesis ii right parenthesis

Differentiating space both space sides space of space the space equation space left parenthesis straight i right parenthesis comma space we space have comma

straight x space left parenthesis negative sin space left parenthesis straight a space plus space straight y right parenthesis right parenthesis space dy over dx equals space minus space cos space left parenthesis straight a plus straight y right parenthesis space equals negative sin space straight y space dy over dx

rightwards double arrow space space open square brackets sin space straight y minus space straight x space sin space left parenthesis straight a space plus space straight y right parenthesis close square brackets dy over dx space equals space minus cos space left parenthesis straight a space plus space straight y right parenthesis

rightwards double arrow space open square brackets sin space straight y space minus fraction numerator cos space straight y over denominator cos space left parenthesis straight a plus straight y right parenthesis end fraction sin space left parenthesis straight a space plus space straight y right parenthesis close square brackets dy over dx space space equals negative cos space left parenthesis straight a space plus space straight y right parenthesis

rightwards double arrow space open square brackets fraction numerator cos space left parenthesis straight a space plus space straight y right parenthesis space space straight x space space sin space straight y space minus space cos space straight y space sin space left parenthesis straight a space plus space straight y right parenthesis over denominator cos space left parenthesis straight a plus straight y right parenthesis end fraction close square brackets dy over dx space equals space minus space cos left parenthesis straight a space plus space straight y right parenthesis space

rightwards double arrow space open square brackets cos space left parenthesis straight a space plus space straight y right parenthesis space straight x space sin space straight y space minus space cosy space space straight x space space sin space left parenthesis straight a space plus space straight y right parenthesis close square brackets dy over dx equals negative cos left parenthesis straight a space plus space straight y right parenthesis space space straight x space space cos space left parenthesis straight a space plus space straight y right parenthesis

rightwards double arrow space space open square brackets sin space left parenthesis straight a space plus space straight y space minus space straight y right parenthesis close square brackets dy over dx space space equals space minus cos squared left parenthesis straight a space plus space straight y right parenthesis space space space space space open square brackets sin left parenthesis straight A minus straight B right parenthesis space equals space sinA space cos space straight B space minus space cosA space sinB close square brackets

rightwards double arrow left square bracket sina space right square bracket space dy over dx equals negative cos squared left parenthesis straight a space plus space straight y right parenthesis

rightwards double arrow space dy over dx space equals fraction numerator negative cos squared left parenthesis straight a space plus space straight y right parenthesis over denominator sin space straight a space end fraction space space space space.. space left parenthesis iii right parenthesis

differentiating space once space again space with space respect space to space straight x space comma we space have comma

sin space straight a space fraction numerator straight d squared straight y over denominator dx squared end fraction space plus space 2 cos left parenthesis straight a space plus space straight y right parenthesis space sin space left parenthesis straight a space plus space straight y right parenthesis dy over dx

rightwards double arrow space sin space straight a space fraction numerator straight d squared straight y over denominator dx squared end fraction space plus space 2 space cos space left parenthesis straight a space plus space straight y right parenthesis space sin space left parenthesis straight a space plus space straight y right parenthesis dy over dx equals 0

rightwards double arrow space sin space straight a space fraction numerator straight d squared straight y over denominator dx squared end fraction space plus space sin space 2 space left parenthesis straight a space plus space straight y right parenthesis dy over dx equals 0

Hence space proved.
1206 Views

Find space dy over dx space if space straight y equals sin to the power of negative 1 end exponent open square brackets fraction numerator 6 straight x minus 4 square root of 1 minus 4 straight x squared end root over denominator 5 end fraction close square brackets

Given space that
straight y space equals space sin to the power of negative 1 end exponent space open square brackets fraction numerator 6 straight x minus 4 square root of 1 space minus space 4 straight x squared end root over denominator 5 end fraction close square brackets

if space straight y space equals space sin to the power of negative 1 end exponent straight x comma space then space dy over dx space equals fraction numerator 1 over denominator square root of 1 minus straight x squared end root end fraction

straight y space equals space sin to the power of negative 1 end exponent open square brackets fraction numerator 6 straight x minus 4 square root of 1 space minus space 4 straight x squared end root over denominator 5 end fraction close square brackets

rightwards double arrow space space straight y space equals space sin to the power of negative 1 end exponent open square brackets fraction numerator 6 straight x over denominator 5 end fraction minus fraction numerator 4 square root of 1 space minus space 4 straight x squared end root over denominator 5 end fraction close square brackets

rightwards double arrow space straight y space equals space sin to the power of negative 1 end exponent open square brackets fraction numerator 2 straight x.3 over denominator 3 end fraction space minus space fraction numerator 4 square root of 1 space minus space left parenthesis 2 straight x right parenthesis squared end root over denominator 5 end fraction close square brackets

rightwards double arrow space straight y space equals space sin to the power of negative 1 end exponent open square brackets 2 straight x.3 over 5 minus 4 over 5 square root of 1 space minus space left parenthesis 2 straight x right parenthesis squared end root close square brackets

rightwards double arrow space straight y space equals space sin to the power of negative 1 end exponent open square brackets 2 straight x space square root of 1 minus open parentheses 4 over 5 close parentheses squared end root minus space 4 over 5 square root of 1 space minus left parenthesis 2 straight x right parenthesis squared end root close square brackets

we space know space that comma

sin to the power of negative 1 end exponent straight p space minus space sin to the power of negative 1 end exponent straight q space equals space sin to the power of negative 1 end exponent space left parenthesis straight p square root of 1 space minus space straight q squared end root minus straight q-th root of 1 space minus space straight p squared end root right parenthesis

Here comma space straight p space equals space 2 straight x space space and space straight q space equals 4 over 5

Differentiating space the space above space functions space with space respect space straight x comma space space we space have comma space

dy over dx space equals space fraction numerator 1 over denominator square root of 1 minus left parenthesis 2 straight x right parenthesis squared end root end fraction space straight x space 2 minus 0

rightwards double arrow space space dy over dx space equals space fraction numerator 2 over denominator square root of 1 minus 4 straight x squared end root end fraction
space
783 Views

Show that the function straight f left parenthesis straight x right parenthesis space equals space open vertical bar straight x minus 3 close vertical bar comma space straight x element of bold R bold comma is  continuous but not differentiable at x=3. 


straight f left parenthesis straight x right parenthesis space equals space open vertical bar straight x minus 3 close vertical bar space equals space open vertical bar table row cell 3 minus straight x comma space space space straight x less than 3 end cell row cell straight x minus 3 comma space straight x greater or equal than 3 end cell end table close vertical bar
Let c be a real number.
Case I: c<3 Then f(c) = 3-c.
limit as straight x rightwards arrow straight c of straight f left parenthesis straight x right parenthesis space equals space limit as straight x rightwards arrow straight c of left parenthesis 3 minus straight x right parenthesis space equals space 3 minus straight c.
Since comma space limit as straight x rightwards arrow straight c of straight f left parenthesis straight x right parenthesis space equals space straight f left parenthesis straight c right parenthesis comma space straight f space is space continous space at space all space negatives space real space numbers.
CaseII: c = 3. Then f(c) = 3 - 3 = 0
limit as straight x rightwards arrow straight c of straight f left parenthesis straight x right parenthesis space equals space limit as straight x rightwards arrow straight c of left parenthesis straight x minus 3 right parenthesis space equals space 3 minus 3 space equals space 0
Since limit as straight x rightwards arrow straight c of straight f left parenthesis straight x right parenthesis space equals space straight f left parenthesis 3 right parenthesis comma space f is continuous at x = 3.

Case III: C>3. Then f(c)  = c - 3
limit as straight x rightwards arrow straight c of straight f left parenthesis straight x right parenthesis space equals space limit as straight x rightwards arrow straight c of left parenthesis straight x minus 3 right parenthesis space equals space straight c minus 3.
Since, limit as straight x rightwards arrow straight c of left parenthesis straight x minus 3 right parenthesis space equals space straight c minus 3.
Therefore, f is a continuous function. 
Now, we need to show that straight f left parenthesis straight x right parenthesis space equals space open vertical bar straight x minus 3 close vertical bar comma space straight x space element of space bold R bold space is space not space differentiable space at space straight x space equals space 3.
Consider the left hand limit of f at x = 3
limit as straight h rightwards arrow 0 to the power of minus of fraction numerator straight f left parenthesis 3 plus straight h right parenthesis minus straight f left parenthesis 3 right parenthesis over denominator straight h end fraction space equals space limit as straight h rightwards arrow 0 to the power of minus of fraction numerator open vertical bar 3 plus straight h minus 3 close vertical bar minus open vertical bar 3 minus 3 close vertical bar over denominator straight h end fraction equals limit as straight h rightwards arrow 0 to the power of minus of fraction numerator open vertical bar straight h close vertical bar minus 0 over denominator straight h end fraction equals limit as straight h rightwards arrow 0 to the power of minus of fraction numerator negative straight h over denominator straight h end fraction equals 1
left parenthesis straight h less than 0 space rightwards double arrow space open vertical bar straight h close vertical bar space equals space minus straight h right parenthesis

Consider the right hand limit of f at x = 3

limit as straight h rightwards arrow 0 to the power of plus of fraction numerator straight f left parenthesis 3 plus straight h right parenthesis minus straight f left parenthesis 3 right parenthesis over denominator straight h end fraction limit as straight h rightwards arrow 0 to the power of plus of fraction numerator open vertical bar 3 plus straight h minus 3 close vertical bar minus open vertical bar 3 minus 3 close vertical bar over denominator straight h end fraction space equals limit as straight h rightwards arrow 0 to the power of plus of fraction numerator open vertical bar straight h close vertical bar minus 0 over denominator straight h end fraction equals limit as straight h rightwards arrow 0 to the power of plus of straight h over straight h equals 1
left parenthesis straight h greater than 0 space rightwards double arrow space open vertical bar straight h close vertical bar space equals space straight h right parenthesis
Since the left and right hand limits are not equal, f is not differentiable at x = 3.
281 Views

limit as straight n rightwards arrow infinity of space open parentheses fraction numerator left parenthesis straight n plus 1 right parenthesis left parenthesis straight n plus 2 right parenthesis....3 straight n over denominator straight n to the power of 2 straight n end exponent end fraction close parentheses to the power of 1 divided by straight n end exponent is equal to
  • 18/e4

  • 27/e2

  • 9/e2

  • 9/e2


B.

27/e2

Let space straight I space equals space limit as straight n stack rightwards arrow infinity with space on top of open parentheses fraction numerator left parenthesis straight n plus 1 right parenthesis. left parenthesis straight n plus 2 right parenthesis..... left parenthesis 3 straight n right parenthesis over denominator straight n to the power of 2 straight n end exponent end fraction close parentheses to the power of 1 over straight n end exponent
space equals space space limit as straight n stack rightwards arrow infinity with space on top of open parentheses fraction numerator left parenthesis straight n plus 1 right parenthesis. left parenthesis straight n plus 2 right parenthesis..... left parenthesis straight n plus 2 straight n right parenthesis over denominator straight n to the power of 2 straight n end exponent end fraction close parentheses to the power of 1 over straight n end exponent

equals space limit as straight n stack rightwards arrow infinity with space on top of open square brackets open parentheses fraction numerator straight n plus 1 over denominator straight n end fraction close parentheses plus open parentheses fraction numerator straight n plus 2 over denominator straight n end fraction close parentheses.... open parentheses fraction numerator straight n plus 2 straight n over denominator straight n end fraction close parentheses close square brackets to the power of 1 over straight n end exponent

taking space log space on space both space sides space comma we space get
log space straight I space equals space limit as straight n stack rightwards arrow infinity with space on top of open square brackets log space open curly brackets open parentheses 1 plus 1 over straight n close parentheses open parentheses 1 plus 2 over straight n close parentheses.... open parentheses 1 plus fraction numerator 2 straight n over denominator straight n end fraction close parentheses close curly brackets close square brackets
rightwards double arrow space log space straight I space equals space limit as straight n stack rightwards arrow infinity with space on top of 1 over straight n open square brackets log open parentheses 1 plus 1 over straight n close parentheses plus space log space open parentheses 1 plus 2 over straight n close parentheses space plus..... plus space log space open parentheses 1 plus fraction numerator 2 straight n over denominator straight n end fraction close parentheses close square brackets
rightwards double arrow space log space straight I space equals limit as straight n stack rightwards arrow infinity with space on top of 1 over straight n sum from straight r space equals 1 to 2 straight n of space log space open parentheses 1 plus straight r over straight n close parentheses
rightwards double arrow space log space straight I space equals space integral subscript 0 superscript 2 space log space left parenthesis 1 plus straight x right parenthesis space dx
rightwards double arrow space log space straight I space equals space open square brackets log space space left parenthesis 1 space plus straight x right parenthesis. straight x space minus space integral fraction numerator 1 over denominator 1 plus straight x end fraction. straight x space dx close square brackets subscript 0 superscript 2
rightwards double arrow space log space space straight I space equals space left square bracket log space left parenthesis 1 space plus straight x right parenthesis. straight x right square bracket subscript 0 superscript 2 space minus integral subscript 0 superscript 2 open parentheses 1 minus fraction numerator 1 over denominator 1 plus straight x end fraction close parentheses dx
rightwards double arrow space log space space straight I space equals space 2. space log space 3 space minus space left square bracket straight x minus log space vertical line 1 plus straight x vertical line subscript 0 superscript 2
rightwards double arrow space log space space straight I space equals space 3. space log space 3 space minus 2
rightwards double arrow space log space space straight I space equals space space log space 27 space minus 2
therefore comma space straight l space equals space straight e to the power of log space 27 minus 2 end exponent space equals space 27. straight e to the power of negative 2 end exponent space equals space 27 over straight e squared
303 Views

Advertisement