# How to Do Trigonometric Functions & Identities

By Rachel KaploveTrigonometric functions and identities apply to a right triangle, so that's a triangle with a 90 degree angle. Do trigonometric functions and identities with help from a professional private tutor in this free video clip.

### Transcript

Hi, I'm Rachel, and today we're going to be going over how to do trigonometric functions and identities. Trigonometric functions and identities apply to a right triangle, so that's a triangle with a 90 degree angle. And first let's go over the functions. If we have theta here, that's this angle, we're going to look for the sin, the cosin and the tangent. Those are the three main things I'm trigonometry. So, we're going to remember that by SOH, soh, CAH, cah, TOA, remember SOHCAHTOA. This stands for sin, which is the opposite over the hypotenuse. CAH is the cosin, which is the adjacent, so that means the leg adjacent to the angle over the hypotenuse, which is this. And TOA, tangent, which is going to be the opposite leg, O, over the adjacent leg, A. So those are the three main parts that we have to remember for trigonometric functions, sin, cosin and tangent. You can remember that by SOHCAHTOA. Now for the identities. There's a plethora of different identities. One main one i the Pythagorean identity, which we write as sin-squared plus cosin-squared equals one. That's a great one to remember. There's also ones like the cosecant, which we abbreviate like CSC, is the reciprocal of sin, it's one over sin. There's also secant, which is the reciprocal of cosecant of cosin, one over cosin, and cotangent, which is, we abbreviate it as COT, and it's one over tangent. And those are just a few examples of trigonometric identities, but here gives you the general basis of what you're looking for in trigonometry. I'm Rachel, and thank you for learning with me today.