NTA Abhyas JEE Main2020MathematicsDifferentiationPractice
If f x = 2 sin ⁡ x - 1 - 2 cot ⁡ x , then the value of f ' π 3 is equal to
Options
- A0
- B- 5 3
- C5 3
- D8 3
Correct answer
C. 5 3
Step-by-step solution
In the neighbourhood of x = π 3 , we know, 2 sin ⁡ x - 1 > 0 ⇒ f x = 2 sin ⁡ x - 1 - 2 cot ⁡ x Now, for the neighbourhood of x = π 3 2 sin ⁡ x - 1 - 2 cot ⁡ x = 2 3 2 - 1 - 2 3 = 3 - 2 3 - 1 = 1 3 - 1 < 0 ∴ f x = 2 cot ⁡ x - 2 sin ⁡ x - 1 Now, f ' x = 2 - c o s e c 2 x - 2 cos ⁡ x f ' π 3 = 2 - 2 3 2 - 2 1 2 = 2 4 3 - 1 = 5 3