The unit circle is labeled using the radian angle system, because the unit circle visualizes the output of the trigononometric functions and the trigonometric functions use radian angles as input. While degrees are sometimes also included, radians are the preferred unit for measuring angles in math^{[1]}.
Radians measure angle as the ratio of the angle’s arclength over the radius of a circle. A full rotation in radians is equal to (tau) radians. Since the unit circle has a radius , angles measured in radians on the unit circle have the unique property that their arclength is equal to their measured value. The interactive above visualizes a full rotation in radians.
The two charts below show common angles measured in radians on the unit circle and their corresponding points. The angles on the first chart are formed by dividing the unit circle into equal parts.
The angles on the second chart are formed by dividing the unit circle into equal parts.
The unit circle is a circle of radius one placed at the origin of the coordinate system. This article discusses how the unit circle represents the output of the trigonometric functions for all real numbers.
Radians are a unit that measure angle using the radius of a circle. One radian is equal to the amount of rotation required to travel the length of one radius along the circumference of the circle.
There are six trigonometric functions that relate to the geometry of the righttriangle sine, cosine, tangent, cosecant, secant, and cotangent. The functions take the angle of a right triangle as input and return a ratio of two of its sides.
The circle constant τ (tau) is a geometric constant approximately equal to 6.283. The numeric value is defined as the length of any circle's circumference divided by the length of its radius.

Radians Versus DegreesWumbo (internal)