a, b, c are the lengths of three sides of a triangle ABC. If a,

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41.

a, b, c are the lengths of three sides of a triangle ABC. If a, b, c are related by the relation a2 + b2 + c2 = ab + bc + ca, then the value of sin2A+ sin2B + sin2C is

  • 3 over 4
  • fraction numerator 3 square root of 3 over denominator 2 end fraction
  • 3 over 2
  • 3 over 2


D.

3 over 2
straight a squared plus straight b squared plus straight c squared space equals space ab space plus space bc space plus space ca
rightwards double arrow space space 2 straight a squared space plus space 2 straight b squared space plus space 2 straight c squared space space equals space 2 ab space plus space 2 bc space plus space 2 ca
rightwards double arrow space straight a squared plus space straight a squared space plus space straight b squared space plus space straight b squared space plus space straight c squared space plus space straight c squared space minus space 2 ab space minus space 2 bc minus space 2 ca space equals space 0
rightwards double arrow space space straight a squared plus straight b squared minus 2 ab space plus space straight b squared plus straight c squared minus 2 bc space plus space straight c squared space plus space straight a squared space minus space 2 ca space equals space 0
rightwards double arrow space left parenthesis straight a minus straight b right parenthesis squared space plus space left parenthesis straight b minus straight c right parenthesis squared space plus space left parenthesis straight c minus straight a right parenthesis squared space equals space 0
rightwards double arrow space space space straight a space minus space straight b space equals space 0 space space space rightwards double arrow space space straight a space equals space straight b

     straight b minus straight c space equals space 0 space space space rightwards double arrow space space straight b space equals space straight c
straight c space minus space straight a space equals space 0 space rightwards double arrow space straight c space equals space straight a
Δ ABC is an equilateral triangle.
therefore space space angle straight A space equals space angle straight B space equals space angle straight C space equals space 60 degree
therefore space sin squared straight A space plus space sin squared straight B space plus space sin squared straight C
equals space 3 sin squared straight A space plus space sin squared straight B space plus space sin squared straight C
equals space 3 space sin squared straight A space space equals space 3 space cross times space sin squared 60 degree
equals space 3 space cross times space open parentheses fraction numerator square root of 3 over denominator 2 end fraction close parentheses squared
equals space fraction numerator 3 space cross times space 3 over denominator 4 end fraction space equals space 9 over 4



 
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42.

The value of straight theta space left parenthesis 0 space less or equal than space straight theta space less or equal than space 90 degree right parenthesis satisfying 2 space sin squared straight theta space equals space 3 space cosθ is

  • 60 degree
  • 30 degree
  • 90 degree
  • 90 degree
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43.

If tan space straight x space equals space sin space 45 degree. space cos space 45 degree space plus space sin space 30 degree then the value of x is

  • 30 degree
  • 45 degree
  • 60 degree
  • 60 degree
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44.

For any real values of θ, fraction numerator square root of secθ space minus 1 end root over denominator square root of secθ space plus 1 end root end fraction space equals space ?

  • cot space straight theta space minus space cosec space straight theta
  • secθ space minus space tanθ
  • cosecθ space minus space cotθ
  • cosecθ space minus space cotθ
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45.

If sin 3A = cos (A - 26°), where 3A is an acute angle then the value of A is

  • 29°

  • 26°

  • 23°

  • 23°

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46.

Find the value of sec squared straight theta space minus space fraction numerator sin squared straight theta space minus space 2 sin to the power of 4 straight theta over denominator 2 cos to the power of 4 straight theta space minus space cos squared straight theta end fraction

  • 1

  • 2

  • -1

  • -1

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47.

If x = a(sinθ + cosθ),  y = b(sinθ - cosθ) then the value of straight x squared over straight a squared space plus space straight y squared over straight b squared is

  • 0

  • 1

  • 2

  • 2

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48.

If sin 5θ = cos 20° (0° < θ < 90°) then the value of θ is

  • 22°

  • 10°

  • 10°

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49.

ABCD is a rectangle of which AC is a diagonal. The value of  is

  • 2

  • 1/4

  • 1

  • 1/2

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50.

In a Δ ABC,  angle straight B space equals space straight pi over 3 comma space space angle straight C space equals space straight pi over 4 and D divides BC internally in the ratio 1 : 3 then fraction numerator sin space angle BAD over denominator sin space angle CAD end fraction is equal to

  • fraction numerator 1 over denominator square root of 2 end fraction
  • fraction numerator 1 over denominator square root of 3 end fraction
  • fraction numerator 1 over denominator square root of 6 end fraction
  • fraction numerator 1 over denominator square root of 6 end fraction
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