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\(\begin{vmatrix} \cos x& \sin x \\ \sin x& \cos x \end{vmatrix}\) = ?

  1. sin 2x
  2. cos 2x
  3. tan 2x
  4. 1

Answer (Detailed Solution Below)

Option 2 : cos 2x
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Detailed Solution

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Calculation:

A = \(\begin{vmatrix} \cos x& \sin x \\ \sin x& \cos x \end{vmatrix}\)

A = cos2 x - sin2 x

A = cos 2x

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