Question: is cos x an even or odd function?
Answer: We're now ready to look at sine and cosine as functions. Sine is an odd function, and cosine is an even function. You may not have come across these adjectives “odd” and “even” when applied to functions, but it's important to know them. A function f is said to be an odd function if for any number x, f(–x) = –f(x).