□ΑBΓΔ、α、β、γ、δ 、∠ ΑBΓ = θ
S = √ s(s-α)(s-β)(s-√α2+ β2-2αβcosθ) + √ s'(s'-γ)(s'-δ)(s'-√α2+ β2-2αβcosθ)
s = α+β+√α2+ β2-2αβ cosθ/2
s' = γ+δ+2s-(α+β)/2
T.theodor 2022.7.14
□ΑBΓΔ、α、β、γ、δ 、∠ ΑBΓ = θ
S = √ s(s-α)(s-β)(s-√α2+ β2-2αβcosθ) + √ s'(s'-γ)(s'-δ)(s'-√α2+ β2-2αβcosθ)
s = α+β+√α2+ β2-2αβ cosθ/2
s' = γ+δ+2s-(α+β)/2
T.theodor 2022.7.14