Question

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

Answer 1

Ответ:

0

Пошаговое объяснение:

$cos2alpha=cos^{2}alpha-sin^{2}alpha =2*cos^{2}alpha -1=1-2*sin^{2}alpha$

- формула косинус двойного аргумента

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

Answer 2

А куда квадрат косинуса делся?

Answer 3

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