What is cosinussatz?

The cosine law, also known as the cosinusssatz, is a mathematical formula used to calculate the length of one side of a triangle when the lengths of the other two sides and the angle between them are known. The formula is as follows:

a² = b² + c² - 2bc cos(A)

where a is the length of the side opposite the angle A, and b and c are the lengths of the other two sides. The cosine law is often used in trigonometry and applied in mathematics, physics, engineering, and other fields to solve problems involving triangles. It can also be used to determine angles in a triangle when the lengths of all sides are known.