Question

корень из 2 * sin 13 pi/8* cos 13pi/8

Answer 1

$\sqrt{2}sin(13 \pi /8)*cos(13 \pi /8)= \frac{ \sqrt{2} }{2}*(2sin(13 \pi /8)*cos(13 \pi /8))=\\\\= \frac{ \sqrt{2} }{2}*sin(2*13 \pi /8)= \frac{ \sqrt{2} }{2}sin(13 \pi /4)= \frac{ \sqrt{2} }{2}*(- \frac{ \sqrt{2} }{2})=- \frac{2}{4}=- \frac{1}{2}$