high School⏱ 4 min

Law of Cosines

c² = a² + b² - 2ab·cos(C)

○Not Started
a = 3.0c = 2.78b = 2.5C=60°ABC
a = 3.0
b = 2.5
C = 60°
c2=a2+b2−2abcos⁡Cc^2 = a^2 + b^2 - 2ab\cos C
c=1202+1002−2⋅120⋅100⋅cos⁡60°=111.4c = \sqrt{120^2+100^2-2\cdot120\cdot100\cdot\cos60°} = 111.4

The law of cosines generalises the Pythagorean theorem. If C=90°, cos90°=0 and the formula reduces to c²=a²+b². Works for any triangle.