How to find the angle measure of an isosceles triangle if you only know the side lengths?

Hello Tbeck227, how to find the angle measure of an isosceles triangle if you only know the side lengths is, for all the angles, though it would be unreasonable to use it for all three, since once we know two the third is easy. Lubin suggested using the Cosine Law for the first calculation and the Sine Law for the second. This is faster than Cosine Law done twice. The suggestion is to use the Cosine Law to determine the angle opposite a largest side.