Law of Sines
We saw that the cosines and the sines were useful in solving parts of an oblique triangle if certain other parts are known. The question here is "why are those laws valid?"
An oblique triangle is one which contains no right angles. The angles from smallest to largest are generally labeled with the uppercase letters as A, B and C and each side opposite those angles is labeled with the corresponding lowercase letters a, b and c.
The Law of Sines and the Law of Cosines are usually applied in non-right triangles. The table below describes the cases and the laws that must be used to solve for the other parts of the triangle.
Learn more about the law of sines by reading the explanation below.
Practice: Answer the following exercises about law of sines.