Định lý cosin

a² = b² + c² - 2bc cosA
b² = a² + c² - 2ac cosB
c² = a² + b² - 2ab cosC

A = (-0.1580772971305559, 1.1360859237541305)
B = (-0.9197086917245382, -0.20459399686678345)
C = (1.3338855717316285, -0.18894403670389343)
đa giác1, c, a, b = Polygon(A, B, C)
α = Angle(B, A, C)