What Are the Trigonometric Functions?

Trigonometric functions have many uses in models for periodical phenomena like temperature changes, planetary orbits, and the rhythm of the heart. Being familiar with trigonometric models give you a better understanding of these, and many other, phenomena.

The three trigonometric functions you need to learn are sine ($\sin x$), cosine ($\cos x$) and tangent ($\tan x$). Here is a picture of what their graphs look like. Notice how the graphs of sine and cosine have the same shape, they are just shifted relative to each other.

The period of $\sin x$ and $\cos x$ is $2\pi$ ($360$°), while $\tan x$ has a period of $\pi$ $(180\text{°})$.