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JEE Main20199 Jan 2019Evening ShiftMathematicsDifferentiationActual

If x = 3 t a n t and y = 3 s e c t , then the value of d 2 y d x 2 at t = π 4 , is:

Options

  1. A1 6
  2. B1 6 2
  3. C1 3 2
  4. D3 2 2

Correct answer

B. 1 6 2

Step-by-step solution

Given x = 3 tan t and y = 3 sec t ⇒ d x d t = 3 sec 2 t and d y d t = 3 sec t tan t ⇒ d y d x = d y d t d x d t ⇒ d y d x = sin t ⇒ d 2 y d x 2 = cos t · d t d x = cos t   · cos 2 t 3 = cos 3 t 3 At t = π 4 d 2 y d x 2 = 1 6 2

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