You have indubitably have encountered geometry and trigonometry before, and may have hoped to never see them again. SURPRISE! Geometry and trigonometry once again rear their heads in physics. You will often be working in two dimensions, in which case the Pythagorean theorem describes the shortest distance between points. In these cases, you will need to solve for the rest of the triangle using SOHCAHTOA. In other situations you will be given a physical scenario that returns to its original configuration with some regularity (such as a pendulum). This returning to original configuration is called "periodicity". In these cases, you will be using a circle to describe the periodicity. As you will recall from previous studies, circles can be described by triangles via $\sin^2{x}+\cos^2{x} = 1$. This is akin to the Pythagorean theorem.