Kosinilause

Kosinilause, also known as the Law of Cosines, is a fundamental theorem in trigonometry that relates the lengths of the sides of a triangle to the cosine of one of its angles. It is particularly useful in solving triangles where the lengths of two sides and the included angle are known, or where the lengths of all three sides are known. The theorem states that for any triangle with sides of lengths a, b, and c, and the angle opposite side c being γ (gamma), the following equation holds:

c^2 = a^2 + b^2 - 2ab * cos(γ)

This equation can be rearranged to solve for any of the sides or the angle, depending on the information available. The Law of Cosines is a generalization of the Pythagorean theorem, which only applies to right-angled triangles. It is widely used in various fields, including geometry, navigation, and engineering, for calculating distances, angles, and other geometric properties. The theorem is named after the ancient Greek mathematician, Cosinus, who first formulated it.