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Question #40953

Difficulty: 8/10 | 🟢 Free

The Question

Let f(x)=arcsin⁡(3sin⁡(2x)+4cos⁡(2x)5)+arccos⁡(5cos⁡(3x)−12sin⁡(3x)13)f(x) = \arcsin\left( \frac{3\sin(2x) + 4\cos(2x)}{5} \right) + \arccos\left( \frac{5\cos(3x) - 12\sin(3x)}{13} \right). Find the value of f′(π2)f'\left( \frac{\pi}{2} \right).

Options

  • A.

    5

  • B.

    1

  • C.

    -1

  • D.

    -5

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Bridge

Practice problems that bridge the gap between foundational theory and advanced practical application.

Concepts Behind This Question

Chain Rule Complexity|The Sum-Difference Formula Constraints|ASTC Quadrant Sign Convention

Why This Question Is Tricky

Common Mistakes

This question tests the student's ability to navigate the chain rule in conjunction with the branch cuts of inverse trigonometric functions.

A common lethal mistake is blindly applying the identities arcsin⁡(sin⁡θ)=θ\arcsin(\sin \theta) = \theta and arccos⁡(cos⁡θ)=θ\arccos(\cos \theta) = \theta, which incorrectly yields a derivative of 55.

By evaluating the arguments at x=π/2x = \pi/2, the sum-difference formulas push the angles into the third and fourth quadrants respectively.

Students must apply the ASTC quadrant sign convention to select the correct branches: π−θ\pi - \theta for arcsin and 2π−θ2\pi - \theta for arccos, which flips the signs of both derivatives, resulting in −5-5.

Quick Facts About This Question

Question Information

SubjectMathematics
ChapterLimits and Derivatives - Class 11
ConceptChain Rule Complexity
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree