Let the domain of function be symmetric about the origin . If , there is always
,
Then is called an even function; if , there is always
,
Then is called an odd function.
The graph of an even function is symmetrical about axis (see Figure 1) . The graph of an odd function is symmetrical about the origin ( see Figure 2).
Figure 1： [ Animation ]
Figure 2： [ Animation ]
For example, function
, ,
is an odd function [ animation ], and are even functions[ animation ].
