Measuring Angles in Trigonometry


In trigonometry, angles are measured in the same units as in geometry—in degrees and radians.

However, in trigonometry the angle of rotation is not limited to the range of 0 to 180 degrees, as in geometry, and can be positive or negative. Therefore, an angle in trigonometry can be expressed in degrees by any real number within the range of minus infinity to plus infinity.

Angles in trigonometry are denoted by lowercase Greek letters: α, β, γ, etc.

Definition of a radian


A radian is an angle corresponding to the arc whose length equals its radius.

Radians are units for measuring angles.

The radian is a central angle whose length of the arc equals the radius of the circle.

Definition of a radian

Definition of a radian