Question

已知cosacosb=sinasinb=0,那么sinacosb-cosasinb的值为?

Answer 1

因为

cosacosb=sinasinb=0,

所以

cos(a-b)=cosacosb+sinasinb=0.

由

sin^2 (a-b)+cos^2 (a-b)=1

得

sin(a-b)=1或-1.

即

sinacosb-cosasinb=1或-1.