熱心網友
|sinA|=|sinAsinB|=|sinA|=1;|sinB|=1并且二者同號.所以cosA=cosB=0---cos(A+B)=cosAcosB-sinAsinB=0-1=-1.
熱心網友
已知：sinAsinB=1求解：cos(A+B)∵sinAsinB=1∴sinA,sinB同正或同負(±1)∴cosA,cosB均為0即cosAcosB=0cos(A+B)=cosAcosB-sinAsinB=0-1=-1
|sinA|=|sinAsinB|=|sinA|=1;|sinB|=1并且二者同號.所以cosA=cosB=0---cos(A+B)=cosAcosB-sinAsinB=0-1=-1.
已知：sinAsinB=1求解：cos(A+B)∵sinAsinB=1∴sinA,sinB同正或同負(±1)∴cosA,cosB均為0即cosAcosB=0cos(A+B)=cosAcosB-sinAsinB=0-1=-1