Law of Cosines

也称为: Cosine Rule

c^2 = a^2 + b^2 - 2ab\cos(C)

c² = a² + b² - 2ab·cos(C)

它计算什么

Generalizes the Pythagorean theorem to any triangle. When C = 90°, cos(C) = 0 and it reduces to a² + b² = c².

象征	姓名	单元	描述
a, b, c	Sides	—	The three sides of a triangle
C	Angle	degrees/radians	The angle opposite to side c

1c² = 25 + 49 - 2(5)(7)cos(60°)

2c² = 74 - 70(0.5) = 74 - 35 = 39

3c = √39 ≈ 6.24

结果: c ≈ 6.24