The Pythagorean trigonometric identity is a trigonometric identity based on the application of the Pythagorean Theorem to the unit triangle.
The fundamental identity is:
Identity: , for all  


Implications
Due to this fundamental relationship, other Pythagorean Identities emerge through the use of:
 the complimentary and cofunction properties
 the reciprocal functions
 the quotient identities
The other identities include: