已知sin acos b=1,则cos(a+b)=
问题描述:
已知sin acos b=1,则cos(a+b)=
急
答
sin acos b=1sina=1或cosb=1cosa=0,sinb=0cos(a+b)=cosacosb-sinasinb=0-0=0sina=-1,cosb=-1cosa=0,sinb=0 cos(a+b)=cosacosb-sinasinb=0-0=0