若sinasinb=1,则cos(a-b)=?
问题描述:
若sinasinb=1,则cos(a-b)=?
答
sinasinb=1
sin^2a+cos^2a=1
cos(a-b)=cosacosb+sinasinb=cosacosb+1
=cosacosb+sin^2a+cos^2a