" I do understand trigonometry concepts, but I want to know if there is a quick & easy way to  memorize trig identities? Thanks for your help!  "

Like how there are many definitions in the English language, there are many identities in the trig world.

A simple math identity is 4 = 3 + 1. In trigonometry, a simple identity can be tangent = sine/cosine.  Just like how we can group English words into categories, such as nouns, verbs, and adverbs, we can cluster our trigonometric identities into groups.

How  some words in the English language are more popular, some of our trigonometric identities are more commonly used.

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The ones that are the most common have already been categorized into three well-known groups:

1. First we have the basic identities ::  These are your basic definitions of your six trig functions: Trig identities.

2. The second group is called the Pythagorean identities :: These are called Pythagorean because they make use of the Pythagorean theorem, which says that for a right triangle a^2 + b^2 = c^2, where c is the hypotenuse and a and b are the legs: trig identities.

3. The next group is called the angle sum and difference identities :: These tell you how you can break down a trig function that involves the addition or subtraction of two angles.

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