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Let \(A = \begin{pmatrix} 1 & -\tan\theta \\ \tan\theta & 1 \end{pmatrix}\) and \(B = \begin{pmatrix} 1 & \tan\theta \\ -\tan\theta & 1 \end{pmatrix}\). If \(C = AB^{-1}\), then what is \(\det(C)\) equal to?

This question was previously asked in
NDA 2 2026 GAT Question Paper (13-Sep-2026)
The correct answer is

\(1\)

\(\det(A)=1+\tan^2\theta=\sec^2\theta\) and \(\det(B)=1+\tan^2\theta=\sec^2\theta\). Since \(\det(C)=\det(AB^{-1})=\dfrac{\det(A)}{\det(B)}=\dfrac{\sec^2\theta}{\sec^2\theta}=1\).

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Similar Questions

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Important Questions from Evaluation of Determinants

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