# How to Do Trigonometry With Identities

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Doing trigonometry with identities requires you to verify those identities and also be able to simplify expressions. Do trigonometry with identities with help from a mathematics educator in this free video clip.

Part of the Video Series: Trigonometry Education
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## Video Transcript

Hi. I'm Jimmy Chang and we're here to talk about how to do trigonometry with identities. Now in order for you to do that, you want to think about the identity equations that you have to work with, so, and oftentimes you want to use that to kind of verify identities and be able to simplify expressions that you have but the important thing is to do trigonometry with identities, you need to know what those are first. Now there are a couple of examples of identities that you'll be using a lot is sine square theta plus cosine square theta is equal to one. Now this is going to be important, but more often than not in trigonometry, you also want to think about ways to modify this identity. For example, it's good in trigonometry and future courses to think about the fact that based on this fact, that cosine square theta is equal to one minus sine square theta. Similarly, using the original identity, think of sign square theta as one minus cosine theta. But it's not just this particular identity you want to do this with, you want to use this particular identity one plus tangent square theta is equal to secant squared theta. Because you can use this identity to be able to get tangent squared by itself. And similarly, one plus cotangent squared theta, is equal to cosecant square theta. Use the same kind of logic there. So the bottom line is when you do trigonometry with identities, you want to know as many identities as possible so you can algebraically manipulate them into what you need. So I'm Jimmy Chang and that's a brief glimpse on how to do trigonometry using identities.

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