tanB=1/2,tanC=-2所以sinB=√5/5,sinC=2√5/5 cosB=2√5/5 ,cosC=-√5/5sinA=sin(B+C)=sinBcosC+cosBsinC=3/5由正弦定理a/sinA=b/sinB=c/sinC=2Rab/(sinAsinB)=(c/sinC)^2ab=sinAsinB*(c/sinC)^2面积=absinC/2=1=sin...