NTA Abhyas JEE Main2020MathematicsDifferentiationPractice
If x = 1 - t 2 1 + t 2 and y = 2 t 1 + t 2 , t h e n d y d x is equal to
Options
- A- y x
- By x
- C- x y
- Dx y
Correct answer
C. - x y
Step-by-step solution
∵ x = 1 - t 2 1 + t 2   a n d   y = 2 t 1 + t 2 Put t = tan ⁡ θ in both the equations, we get x = 1 - tan 2 ⁡ θ 1 + tan 2 ⁡ θ = cos ⁡ 2 θ ...(i) and y = 2 tan ⁡ θ 1 + tan 2 ⁡ θ = sin ⁡ 2 θ ...(ii) On differentiating both the eqs.(i) and (ii), we get d x d θ = - 2 sin ⁡ 2 θ   a n d   d y d θ = 2 cos ⁡ 2 θ Therefore, d y d x = d y d θ d x d θ = - cos ⁡ 2 θ sin