The law of the cosines involves a triangle where it relates to the angles and not the sides like it does with the Pythagorean Theorem. However, there is also a formula for the law of cosines and it is similar to the formula for the Pythagorean Theorem. It states C squared is equal to A squared plus B squared minus two A times B times the cosine times the measurement of the angle that is between the lines of A and B.
The angle that is labeled is actually situated across from the line with the same letter. The Pythagorean Theorem is a special case of the law of cosines because the formulas are so similar, but the law of cosines can be used for any triangle.