Cosine Rule

The Cosine Rule is a mathematical formula used in triangles to find the length of a side or the measure of an angle when other parts are known. It relates the lengths of two sides and the included angle to the third side: \( c^2 = a^2 + b^2 - 2ab \cos(C) \). Here, \(a\), \(b\), and \(c\) are side lengths, and \(C\) is the angle between sides \(a\) and \(b\). It helps solve triangles that aren’t right-angled, especially in real-world applications like navigation, engineering, and geometry.