在三角形ABC中,cosA=5/-13,cosB=3/5,求(1)sinC的值;(2)设三角形ABC的面积.C=180-(A+B),sinC=sin(A+B)=sinA*cosB+cosA*sinB.cosA=5/-13,sinA=12/13.cosB=3/5,sinB=4/5.sinC=sin(A+B)=sinA*cosB+cosA*sinB.=16/65..为什么由cosA=5/-13,sinA=
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![在三角形ABC中,cosA=5/-13,cosB=3/5,求(1)sinC的值;(2)设三角形ABC的面积.C=180-(A+B),sinC=sin(A+B)=sinA*cosB+cosA*sinB.cosA=5/-13,sinA=12/13.cosB=3/5,sinB=4/5.sinC=sin(A+B)=sinA*cosB+cosA*sinB.=16/65..为什么由cosA=5/-13,sinA=](/uploads/image/z/446140-28-0.jpg?t=%E5%9C%A8%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E4%B8%AD%2CcosA%3D5%2F-13%2CcosB%3D3%2F5%2C%E6%B1%82%EF%BC%881%EF%BC%89sinC%E7%9A%84%E5%80%BC%EF%BC%9B%EF%BC%882%EF%BC%89%E8%AE%BE%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E7%9A%84%E9%9D%A2%E7%A7%AF.C%3D180-%28A%2BB%29%2CsinC%3Dsin%28A%2BB%29%3DsinA%2AcosB%2BcosA%2AsinB.cosA%3D5%2F-13%2CsinA%3D12%2F13.cosB%3D3%2F5%2CsinB%3D4%2F5.sinC%3Dsin%28A%2BB%29%3DsinA%2AcosB%2BcosA%2AsinB.%3D16%2F65..%E4%B8%BA%E4%BB%80%E4%B9%88%E7%94%B1cosA%3D5%2F-13%2CsinA%3D)
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