JEE Main2018MathematicsDifferentiationActual
If x = 2 cosec - 1 t and y = 2 sec - 1 t , t ≥ 1 , then d y d x is equal to
Options
- Ay x
- B- y x
- C- x y
- Dx y
Correct answer
B. - y x
Step-by-step solution
Given, x = 2 cosec - 1 t = 2 cosec - 1 t 2 and y = 2 sec - 1 t = 2 sec - 1 t 2 , then we have x · y = 2 sec − 1 t + cosec − 1 t 2 And, we know that sec - 1 x + cosec - 1 x = π 2 , ⇒ x y = 2 π 4 On differentiating, both sides with respect to x , and applying product rule, we get x d y d x + y = 0 ⇒ d y d x = - y x .