Sine, Cosine and Tangent (also known as sin, cos, and tan when on a calculator)  are ratios of right triangles that are used throughout the unit of Trigonometry.

In an angle, there is a hypotenuse (longest), an opposite side (across from hypotenuse), and a adjacent (the one left over);

To find the Sin, you would divide the opposite side by the hypotenuse.

To find the Cos, you would divide the adjacent by the hypotenuse.

To find  the Tan, you would divide the opposite side by the adjacent.