# Even-Odd Identities in Trigonometric Functions

All functions, including trig functions, can be described as being even, odd, or neither. Knowing whether a trig function is even or odd can help you simplify an expression. These even-odd identities are helpful when you have an expression where the variable inside the trig function is negative (such as –*x*). The even-odd identities are as follows:

sin(–x) = –sinx |
csc(–x) = –cscx |

cos(–x) = cosx |
sec(–x) = secx |

tan(–x) = –tanx |
cot(–x) = –cotx |