步骤1.在锐角△ABC中,设BC=a,AC=b,AB=c.作CH⊥AB垂足为点HCH=a·sinBCH=b·sinA∴a·sinB=b·sinA得到a/sinA=b/sinB同理,在△ABC中,b/sinB=c/sinC 步骤2.证明a/sinA=b/sinB=c/sinC=2R：如图,任意三角形ABC,作ABC的外...