Question

Упростите выражение:
1-cos²α;
sin²α-1;
cos²α+1-sin²α;
(1-cos α)(1+cos α)

Answer 1

1-cos²α=sin²α;
sin²α-1=sin²α-(sin²α+cos²α)=-cos²α;
cos²α+1-sin²α=cos²α+cos²α+sin²α-sin²α=2cos²α;
(1-cosα)(1+cosα)=1-cos²α=sin²α.