Mr.Unit Circle

The "Unit Circle" is a circle with a radius of 1. Frequently, especially in trignometry, the unit circle is the circle of radius one centered at the origin (0, 0). Being simple, it is a way to learn and talk about lengths and angles. The center is put on a graph where the x axis and y axis cross, so we get this neat arrangement here. Because the radius is 1, we can directly measure sine, cosine, and tangent.
For example:
What happens when the angle, θ, is 0°?

• cos 0° = 1, sin 0° = 0 and tan 0° = 0

What happens when θ is 90°?

• cos 90° = 0, sin 90° = 1 and tan 90° is undefined