## Trig Pythagorean Identities

For angle θ at which the functions are defined:

(1) cos

(2) 1 + tan

(3) 1 + cot

^{2}θ + sin^{2}θ = 1(2) 1 + tan

^{2}θ = sec^{2}θ(3) 1 + cot

^{2}θ = csc^{2}θDividing both
sides of the first equation by cos

^{2}θ results in the second equation. Similarly, dividing both sides of the first equation by sin^{2}θ results in the third equation.Other Trigonometric Identities:

- Reciprocal Identities
- Even-Odd Identitites
- Cofunction Identities
- Half-Angle Identities
- Double-Angle Identities

- Sum and Difference Identities
- Sum to Product Identities
- Product to Sum Identities