Question

$2\sqrt{2}* cos^{2} \frac{3\pi }{8} - \sqrt{2}$

Answer 1

Ответ:

0

Пошаговое объяснение:

$cos2\alpha=cos^{2}\alpha-sin^{2}\alpha =2*cos^{2}\alpha -1=1-2*sin^{2}\alpha$

- формула косинус двойного аргумента

$2\sqrt{2} *cos^{2} \frac{3\pi }{8}-\sqrt{2}=\sqrt{2}*(2*cos^{2}\frac{3\pi }{8} -1) =\sqrt{2} *cos(2*\frac{3\pi }{8}) =\sqrt{2}*cos\frac{3\pi }{2}=\sqrt{2}*0=0$

Answer 2

$2 \sqrt{2} \cos {}^{2} ( \frac{3\pi}{8} ) - \sqrt{2} = \sqrt{2} (2 \cos {}^{2} ( \frac{3\pi}{8} ) - 1) = \sqrt{2} \cos(2 \times \frac{3\pi}{8} ) = \sqrt{2} \times \cos( \frac{3\pi}{2} ) = \sqrt{2} \times 0 = 0$