Answer:
[tex]the \: equation \: is \: equivalent \: to \\ 2 \: { \sin }^{2} (( \: \frac{\pi}{2}) \: {cos}^{2} x ) = \\ \: 2 \: {sin}^{2} (( \frac{\pi}{2} sin \: 2x \: ) \\ = {cos}^{2} x = sin \: 2x \\ = \: \cos \: x(cos \: x \: - \: 2 \: sin \: x) \: = \: 0 \\ = \: 1 - 2 \tan \: x = 0 \: as \: cos \: x \: ≠ 0 \\ x ≠ (2n + 1) \frac{\pi}{2} \\ = \tan(x) = \frac{1}{2} \\ = \cos(2x) = \frac{1 - {tan \: }^{2}x }{1 + {tan \: }^{2} \:x } = \frac{3}{5} [/tex]
