Question

Упростите выражение:

1) cos^2 α-1
2) (sinα + cosα)^2 - 2sin α cos α

Answer 1

$tt 1)~ cos^2alpha-1=-(1-cos^2alpha)=-sin^2alpha\ \ 2)~ (sin alpha+cosalpha)^2-2sinalphacosalpha=1+2sinalphacosalpha-2sinalphacosalpha=1$