Question

cos3П:4+сosП:2+сos(-П:4)+cos(2П)

Answer 1

$cos (3/4 pi)= -frac{sqrt{2}}{2} \ cos (1/2 pi)= 0 \ cos (-1/4 pi)= frac{sqrt{2}}{2} \ cos (2 pi)=1$

сумма = 1