Using principle of mathematical induction, prove that for all

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 Multiple Choice QuestionsLong Answer Type

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21.

Using principle of mathematical induction, prove that

cos space straight alpha space space cos space 2 straight alpha space space cos space 4 straight alpha space............... cos left parenthesis 2 to the power of straight n minus 1 end exponent straight alpha right parenthesis space equals space fraction numerator sin space 2 to the power of straight n straight alpha over denominator 2 to the power of straight n sinα end fraction for all straight n space element of space straight N


Let P(n) : space space cosα space cos 2 straight alpha space cos 4 straight alpha space.......... cos left parenthesis 2 to the power of straight n minus 1 end exponent straight alpha right parenthesis space equals space fraction numerator sin left parenthesis 2 to the power of straight n straight alpha right parenthesis over denominator 2 to the power of straight n sinα end fraction

I.   For n = 1,

    straight P left parenthesis 1 right parenthesis space colon space cosα space equals space fraction numerator sin space 2 straight alpha over denominator 2 sin space straight alpha end fraction rightwards double arrow space cosα space equals space fraction numerator 2 sinα space cosα over denominator 2 space sin space straight alpha end fraction rightwards double arrow space cosα space equals space cos space straight alpha

∴   P(1) is true

II.   Suppose the statement is true for n = m, straight m space element of space straight N

III.  P(m) : cos space straight alpha space space cos 2 straight alpha space cos 4 straight alpha space.......... space cos 2 to the power of straight m minus 1 end exponent space straight alpha space equals space fraction numerator sin space 2 to the power of straight m straight alpha over denominator 2 to the power of straight m sinα end fraction          ... (i)

       For n = m + 1,

       straight P left parenthesis straight m plus 1 right parenthesis space colon space cosα space space cos space 2 straight alpha space cos 2 squared straight alpha space............. space cos left parenthesis 2 to the power of straight m minus 1 end exponent straight alpha right parenthesis space cos space left parenthesis 2 to the power of straight m straight alpha right parenthesis space equals space fraction numerator sin left parenthesis 2 to the power of straight m plus 1 end exponent straight alpha right parenthesis over denominator 2 to the power of straight m plus 1 end exponent sin space straight alpha end fraction

      Now, cos space straight alpha space cos space 2 straight alpha space cos space 2 squared straight alpha space........... space cos left parenthesis 2 to the power of straight m minus 1 end exponent straight alpha right parenthesis space cos left parenthesis 2 to the power of straight m space straight alpha right parenthesis

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             = fraction numerator 2 space sin left parenthesis 2 to the power of straight m straight alpha right parenthesis space cos left parenthesis 2 to the power of straight m straight alpha right parenthesis over denominator 2 to the power of straight m plus 1 end exponent sinα end fraction equals space fraction numerator sin left parenthesis 2.2 to the power of straight m straight alpha right parenthesis over denominator 2 to the power of straight m plus 1 end exponent sinα end fraction equals space fraction numerator sin left parenthesis 2 to the power of straight m plus 1 end exponent straight alpha right parenthesis over denominator 2 to the power of straight m plus 1 end exponent sinα end fraction

∴      P(m + 1) is true.

       P(m) is true rightwards double arrow P(m + 1) is true

Hence, by the principle of mathematical induction, P(n) is true for all straight n space element of space straight N.

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 Multiple Choice QuestionsShort Answer Type

22.

Using principle of mathematical induction, show that straight n less than 2 to the power of straight n space space for space all space straight n space element of space straight N

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23.

Using principle of mathematical induction, show that  3 to the power of straight n greater than 2 to the power of straight n for all straight n space element of space straight N


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 Multiple Choice QuestionsMultiple Choice Questions

24.

If the number of terms in the expansion of open parentheses 1 minus 2 over straight x space plus 4 over straight x squared close parentheses to the power of straight n comma straight x not equal to 0 comma is 28, then the sum of the coefficients of all the terms in this expansion is

  • 64

  • 2187

  • 243

  • 243

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25.

Statement − 1: For every natural number n ≥ 2 fraction numerator 1 over denominator square root of 1 end fraction space plus space fraction numerator 1 over denominator square root of 2 end fraction space plus space..... space plus space fraction numerator 1 over denominator square root of straight n end fraction space greater than space square root of straight n

Statement −2: For every natural number n ≥ 2,straight n greater or equal than 2 comma space square root of straight n left parenthesis straight n plus 1 right parenthesis space end root space less than space straight n plus 1

  • Statement −1 is false, Statement −2 is true

  • Statement −1 is true, Statement −2 is true, Statement −2 is a correct explanation for Statement −1

  • Statement −1 is true, Statement −2 is true; Statement −2 is not a correct explanation for Statement −1.

  • Statement −1 is true, Statement −2 is true; Statement −2 is not a correct explanation for Statement −1.

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26.

If A = open square brackets table row 1 0 row 1 1 end table close square brackets and I = open square brackets table row 1 0 row 0 1 end table close square brackets , then which one of the following holds for all n ≥ 1, by the principle of mathematical induction

  • An = nA – (n – 1)I

  • An = 2n-1A – (n – 1)I

  • An = nA + (n – 1)I

  • An = nA + (n – 1)I

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27.

Let S(K) = 1 +3+5+..... (2K-1) = 3+K2. Then which of the following is true?

  • S(1) is correct

  • Principle of mathematical induction can be used to prove the formula

  • S(K) ≠S(K+1)

  • S(K) ≠S(K+1)

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28.

Maximum sum of coefficient in the expansion of (1 – x sinθ + x2 )n is

  • 1

  • 2n

  • 3n

  • 3n

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29.

For positive integer n, n3 + 2n is always divisible by

  • 3

  • 7

  • 5

  • 6


30.

The acceleration of a particle starting from rest moving in a straight line with uniform acceleration is 8 m/s2. The time taken by the particle to move the second metre is

  • (√2-1)/2 S

  • (√2+1)/2 S

  • (1 + √2)S

  • (√2-1)S


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