Trigonometric Identities Explained

Description

This video is a review of all the important trig identities. It provides several examples of different trig identities and shows when and how you would have to use them. This video provides content in an organized manner.

Overview

Trigonometric identities, or trig identities, are equations dealing with trig functions that should be memorized. The most common trig functions are sine, cosine, and tangent. Trig identities will help you when you need to simplify equations with trigonometric functions in them. There are a few very important trig identites. Two of these are the Pythagorean trig identity and the Ratio identity.

Pythagorean Trig Identity:

Ratio Identity:

From the Pythagorean trig identity, another identity can be found. This is . There are a few other identities, that are not so much trig identities as factoring for trigonometric functions.

sin(a + b) = [sin(a) * cos(b)] + [sin(b) * cos(a)]

cos(a + b) = [cos(a) * cos(b)] – [sin(a) * sin(b)]

sin(2a) = 2 * sin(a) * cos(a)

cos(2a) = [cos(a)]^2 – [sin(a)]^2

There are many more trig identities, but these are the most important. With these, you will be able to find almost every other trig identity.

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