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Question #41211

Difficulty: 8/10 | 🟢 Free

The Question

Let A(x)A(x) and B(x)B(x) be 3×33 \times 3 matrices defined for x∈(−π2,π2)x \in \left(-\frac{\pi}{2}, \frac{\pi}{2}\right) as follows: A(x)=[x+x2sin⁡(1x)sin⁡xcos⁡x0cos⁡xsin⁡x0−sin⁡xcos⁡x] for x≠0, and A(0)=[001010001]A(x) = \begin{bmatrix} x + x^2 \sin\left(\frac{1}{x}\right) & \sin x & \cos x \\ 0 & \cos x & \sin x \\ 0 & -\sin x & \cos x \end{bmatrix} \text{ for } x \neq 0, \text{ and } A(0) = \begin{bmatrix} 0 & 0 & 1 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{bmatrix} B(x)=[sec⁡xtan⁡x0tan⁡xsec⁡x0001]B(x) = \begin{bmatrix} \sec x & \tan x & 0 \\ \tan x & \sec x & 0 \\ 0 & 0 & 1 \end{bmatrix} If M(x)=(A(x)B(x))TM(x) = (A(x) B(x))^T, then the value of lim⁡x→0det⁡(M(x))e2x−1\lim_{x \to 0} \frac{\det(M(x))}{e^{2x} - 1} is:

Options

  • A.

    12\frac{1}{2}

  • B.

    1

  • C.

    0

  • D.

    \text{Does not exist}

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

Transpose of Product|Differentiation of Determinants|The L'Hôpital's Rule Misuse

Why This Question Is Tricky

Common Mistakes

This question tests the properties of determinants of matrix products and their transposes, combined with a classic calculus trap.

Students often blindly apply L'Hôpital's rule to evaluate the 0/00/0 limit.

However, differentiating the numerator yields 1+2xsin⁡(1/x)−cos⁡(1/x)1 + 2x \sin(1/x) - \cos(1/x), which oscillates and has no limit as x→0x \to 0.

This leads students to incorrectly conclude that the limit does not exist (Option D).

The trap highlights the L'Hôpital's Rule Misuse: the rule is a sufficient, not necessary, condition.

The limit must be evaluated using standard algebraic manipulation and the Squeeze Theorem.

Quick Facts About This Question

Question Information

SubjectMathematics
ChapterMatrices - Class 12
ConceptTranspose of Product
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree