Trigonometric identities are used to manipulate trig equations in certain ways. Here is a list of them:
The six basic trigonometric functions can be defined using a right triangle:
The six trig functions are sine, cosine, tangent, cosecant, secant, and cotangent. They are abbreviated by using the first three letters of their name (except for cosecant which uses ). They are defined as follows:
From the last section, it is easy to see that the following hold:
Angle Addition Identities
(Otherwise known as sum-to-product identities)
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