cosB/sinA+cosA/sinB=2cosBsinB+cosAsinA=2SinASinBcosBsinB-SinASinB+cosAsinA-SinASinB=0(CosB-SinA)SinB + (CosA-SinB)SinA = 0SinA>0,SinB>0 则(CosB-SinA)=0 CosB=SinA=cos(90-A),B=90-A,A+B=90(CosA-SinB)=0Co...