定理三角形中一角是另一角的两倍的充要条件是这两角中较大角所对边与较小角所对边的平方差等于两角中较小角所对边与第三边的积. The necessary and sufficient condition for a corner of the theorem triangle to be twice that of the other corner is that the squared difference between the opposite side of the larger corner of the two corners and the smaller corner is equal to the product of the opposite side and the third side of the smaller corner of the two corners. .