Question 11
DifferentiationIf y = 2xcos2x − sin2x, find dy/dx when x = π/4.
- A.1
- B.−π
- C.π
- D.−1
Show the answer and explanation
Answer: B (−π)
Explanation
dy/dx = 2cos2x − 4x sin2x − 2cos2x = −4x sin2x. At x = π/4: −4(π/4)(sin π/2) = −π.
If y = 2xcos2x − sin2x, find dy/dx when x = π/4.
Answer: B (−π)
dy/dx = 2cos2x − 4x sin2x − 2cos2x = −4x sin2x. At x = π/4: −4(π/4)(sin π/2) = −π.