Math
The Unit Circle
← All Exhibits
A circle with a radius of exactly one unit, marked with angles around its rim, shows how sine, cosine, and the other trigonometric ratios are really just coordinates of a point moving around a circle.
Additional Information
“Unit” just means the radius is defined as 1 — that’s what makes the coordinates of any point on it equal to the cosine and sine of its angle directly.
A full trip around the unit circle is 360 degrees, or 2π radians — the same rotation measured two different ways.
Sound waves, alternating electric current, and swinging pendulums are all described mathematically using the same circular motion this circle represents.