由椭圆一般方程求解椭圆标准方程参数

椭圆的一般方程:
AX2+ BXY + CY2 + DX + EY + 1 = 0.

椭圆几何中心:
Xc = (BE - 2CD) / (4AD – B2)
Yc = (BD – 2AE) / (4AD – B2)

长轴倾角:θ= 1/2 arctan (B/(A - C))

长短半轴分别为:
a2 = 2(AXc2 + CYc2 + BXcYc - 1) / (A + C + ((A-C)2 + B2)1/2)
b2 = 2(AXc2 + CYc2 + BXcYc - 1) / (A + C - ((A-C)2 + B2)1/2)