6刮杯:在△ABC中正烈定理形知=254.b9B.cMC.bLosA=C. SihB-alos BB:nB(SA=9nc、SmB-SAB、SNB(+sASB=hCSBSin(A+B)=sinc= Sh( ShBCElor Snc70ShB=IB(0元)÷B=2选△ABC是有角三角好