Trigonometric Identities
This is a list of the basic trigonometric identities. You may want to work through a tutorial, with examples and detailed solutions, on Using Trigonometric Identities.
Review of Trigonometric Identities
Pythagoren Identities
-
sin2x + cos2x = 1
-
tan2x + 1 = sec2x
- 1 + cot2x = csc2x
Reciprocal Identities
- csc x = 1 / sin x
- sec x = 1 / cos x
- cot x = 1 / tan x
The Tangent and Cotangent Identities
- tan x = sin x / cos x
- cot x = cos x / sin x
Identities for Negatives
- sin (-x) = - sin x (the sine function is an odd function)
- cos (-x) = cos x (the cosine function is an even function)
- tan (-x) = - tan x (the tangent function is an odd function)
More References and Links
Trigonometric Identities and Their ApplicationsTrigonometric Formulas and Their Applications