|
|
|
|
|
|
The radian is the standard unit of angular measure, used in many areas of mathematics. The length of an arc of a unit circle is numerically equal to the measurement in radians of the angle that it subtends; one radian is just under 57.3 degrees.
1/2 circle or half circle is equal to 360°/2 = 180°. Plural name is helf circles.