in mathematics. The function y = f(x) is said to be even if its value does not change when the sign of the independent variable changes—that is, if f(–x) = f(x). If, however, f(–x) = –f(x), then the function f(x) is said to be odd. For example, y = cos x and y = x2 are even functions, and y = sin x, y = x3 are odd functions. The graph of an even function is symmetric with respect to the y-axis, and the graph of an odd function is symmetric with respect to the origin.