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从著名的正弦定理a/sinA=b/sinB=c/sinC=2R(R为三角形外接圆半径),不难推广而得:a~2-b~2=2Rcsin(A-B),6~2-c~2=2Rasin
From the well-known sine theorem a/sinA=b/sinB=c/sinC=2R (R is the radius of the circumcircle of the triangle), it is not difficult to generalize: a~2-b~2=2Rcsin(AB), 6~2- c~2=2Rasin