### 26.13.4 Measure of an angle in the plane

See Section 27.10.9 for angle measures in 3D geometry.

The angle command finds the measure of an angle.

- angle takes three mandatory arguments and one optional argument:
  - A,B,C, three points.
  - str, a string.
- angle(A,B,C ⟨,str ⟩) returns the measure of angle ABC (in the units that Xcas is configured for). With the argument str, the angle will be drawn indicated by a small arc and labeled with the string. If the angle is a right angle, the indicator will be a corner rather than an arc.

#### Examples

angle(0,1,1+i)

1
4
| π

angle(0,1,1+i,"a")

angle(0,1,1+i,"")

angle(0,1,i,"A")

angle(0,1,i,"A")[0]

1
2
| π

The angle command has angleat and angleatraw versions (see Section 26.13.1). For the command line versions of these commands, the optional fourth argument for angle is replaced by a mandatory fourth argument for the point to put the measurement.

##### Converting between radians and degrees.

You can use radians and degrees commands to convert from degrees to radians and vice versa, respectively. These commands return inexact values.