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.