解答
(a²+b²)sin(A-B)=(a²-b²)sin(A+B)(a²+b²)(sinAcosB-cosAsinB)=(a²-b²)(sinAcosB+cosAsinB)b²sinAcosB=a²cosAsinBsinAsin²BcosB-sin²AcosAsinB=0sinAsinB(sinBcosB-sinAcosA)=0sin2A=sin2B2A=2B或2A=π-2BA=B或A+B=π/2三角形是等腰三角形或直角三角形。
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