已知sin acos b=1,则cos(a+b)=

问题描述:

已知sin acos b=1,则cos(a+b)=

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