The Cosine Rule is a mathematical formula used in trigonometry to find the lengths of sides or angles in a triangle. It states that in any triangle, the square of one side is equal to the sum of the squares of the other two sides minus twice the product of those sides multiplied by the cosine of the included angle. The formula is expressed as c^2 = a^2 + b^2 - 2ab \cdot \cos(C) , where c is the side opposite angle C , and a and b are the other two sides. This rule is particularly useful for non-right triangles, where traditional methods like the Pythagorean Theorem do not apply. It allows for the calculation of unknown side lengths or angles when certain other measurements are known. The Cosine Rule is essential in various fields, including physics, engineering, and computer graphics, where understanding triangle properties is crucial