sina^2+2sinasinb+sinb^2=1cosa^2+2cosacosb+cosb^2=0sina^2+cosa^2+2sinasinb+2cosacosb+sinb^2+cosb^2=11+2sinasinb+2cosacosb+1=1sinasinb+cosacosb=-1/2cos(a-b)=-1/2sin(a-b)=±根号3/2tan(a-b)=±根号3a-b=±...