NTA Abhyas JEE Main2020MathematicsDifferentiationPractice
If the function f x = cos - 1 x 3 2 - 1 - x - x 2 + x 3 (where, ∀ 0 < x < 1 ), then the value of 3 f ' 1 2 is equal to (take 3 = 1.73 )
Correct answer
3.73
Step-by-step solution
f x = cos - 1 x x - 1 - x 1 - x 2 = cos - 1 x x - 1 - x 2 1 - x 2 = cos - 1 x + cos - 1 x Now, f ′ x = − 1 1 − x 2 − 1 1 − x ⋅ 1 2 x f ' 1 2 = − 1 1 − 1 4 − 1 1 2 × 1 2 1 2 = − 2 3 − 1 3 f ' 1 2 = - 3 − 2 3 − 1 = 3 . 73