圆内接不规则四边形公式:
e = √ (ac+bd) * (ad+bc) / (ab+cd)
f = √ (ab+cd) * (ac+bd) / (ad+bc)
a * c + b * d = e * f (托勒密定理)
α = arccos( (a²+d²-b²-c²) / (2*(ad+bc)) )
δ = arccos( (d²+c²-a²-b²) / (2*(dc+ab)) )
β = 180° - δ
γ = 180° - α
p = a + b + c + d
半周长s = p / 2
A = √ (s-a) * (s-b) * (s-c) * (s-d)
rc = 1/(4*A) * √ (ab+cd) * (ac+bd) * (ad+bc)
请看 圆内接不规则四边形计算器
