The tangent of an angle is the trigonometric ratio between the adjacent side and the opposite side of a right triangle containing that angle.
In the triangle shown, and .
The tangent ratio is the same regardless of the size of the right triangle. So, it is often easiest to consider a right triangle with a hypotenuse of length 1.
The tangent ratio can also be thought of as a function, which takes different values depending on the measure of the angle. You can measure an angle in degrees or radians.