When applying the Law of Cosines, which side does 'a' refer to in the formula a² = b² + c² - 2bc Cos A?

In the Law of Cosines, the formula ( a^2 = b^2 + c^2 - 2bc \cos A ) provides a relationship between the lengths of the sides of a triangle and the cosine of one of its angles. In this formula, the variable ( a ) specifically represents the length of the side that is opposite angle ( A ).

This relationship is crucial because the Law of Cosines is designed to generalize the Pythagorean theorem for cases where the triangle is not a right triangle. By indicating which side corresponds to which angle, the formula allows for the calculation of one side given the other two sides and the angle opposite to the desired side.

Therefore, when using the Law of Cosines, recognizing that ( a ) is the side opposite angle ( A ) is essential for applying the formula correctly and successfully solving problems related to triangles.