△ABC中,(a^2+b^2)sin(A-B)=(a^2-b^2)sin(A+B),试判断△ABC的形状。答案是这样写的:由题知:

2025-06-23 22:54:56
推荐回答(1个)
回答1:

解sin(A+B)-sin(A-B)=sinAcosB+cosAsinB-(sinAcosB-cosAsinB)=2cosAsinB
即sin(A+B)+sin(A-B)=sinAcosB+cosAsinB+(sinAcosB-cosAsinB)=2sinAcosB
即a^2[sin(A+B)-sin(A-B)]=b^2[sin(A+B)+sin(A-B)]
得 a^2sosAsinB=b^2sinAcosB