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Evaluate : \(\begin{vmatrix}cos\,15° & \ sin\,15° \\[0.3em]sin\,75° & cos\,75° \\[0.3em]\end{vmatrix}\) |
Answer» Expanding the determinant, we get cos 15°. cos 75° – sin 15°. sin 75° = cos (15° + 75°) = cos 90° = 0 [Note: cos (A + B) = cos A. cos B – sin A. sin B] |
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