# What Are the Trigonometric Functions?

Trigonometric functions have many uses in models for periodical phenomena like temperature changes, the planet’s orbits around the sun and the rhythm of the heart. Being familiar with trigonometric models give you a better understanding of phenomena like that.

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

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