Question

3 sqrt 2- cos^2*5пи/8 помогите пожалуйста.

Answer 1

$3 \sqrt{2} -cos^2 \frac{5 \pi }{8} =3 \sqrt{2} -cos^2( \frac{ \pi }{2} + \frac{ \pi }{8} )=3 \sqrt{2} -sin^2 \frac{ \pi }{8}$$=3 \sqrt{2} - \frac{1-cos \frac{ \pi }{4} }{2} =3 \sqrt{2} - \frac{1- \frac{ \sqrt{2} }{2} }{2} = \frac{12 \sqrt{2} -2+ \sqrt{2} }{4} = \frac{13 \sqrt{2} -2}{4}$