\(π \), then, the value of  \(π... - Solved | MCA Prep" /> \(π \), then, the value of  \(π... - Solved | MCA Prep" /> \(π \), then, the value of 

Question 8

Mathematics Determinants Hard

If A + B + C = <span class="math-tex">\(\pi \)</span>, then, the value of&nbsp;<span class="math-tex">\(\left| {\begin{array}{*{20}{c}} {\sin \left( {A + B + C} \right)}&amp;{\sin B}&amp;{\cos C}\\ { - \sin B}&amp;0&amp;{\tan A}\\ {\cos \left( {A + B} \right)}&amp;{ - \tan A}&amp;0 \end{array}} \right|\)</span>&nbsp;is

(A) 0
(B) 1
(C) 2 sin A sin B
(D) 2
✓ Correct Answer: Option A Verified Solution

📘 Step-by-Step Solution & Detailed Explanation:

Since \(A + B + C = \pi\): \(\sin(A+B+C) = \sin\pi = 0\) and \(\cos(A+B) = \cos(\pi - C) = -\cos C\).

The determinant becomes \(\begin{vmatrix} 0 & \sin B & \cos C \\ -\sin B & 0 & \tan A \\ -\cos C & -\tan A & 0 \end{vmatrix}\)

This is a skew-symmetric matrix of odd order (3×3). The determinant of any such matrix is 0.

(Direct expansion also gives \(-\sin B\tan A\cos C + \cos C\sin B\tan A = 0\).)

Answer: (A) 0

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