The measure of an angle in the plane: angle

### 13.14.4 The measure of an angle in the plane: angle

See Section 14.12.9 for angle measures in three-dimensional 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

- Input:
  angle(0,1,1+i)
  Output:

  1
  4
  | π

- Input:
  angle(0,1,1+i,"a")
  Output:
- Input:
  angle(0,1,1+i,"")
  Output:
- Input:
  angle(0,1,i,"A")
  Output:
- Input:
  angle(0,1,i,"A")[0]
  Output:

  1
  2
  | π

The angle command has angleat and angleatraw versions (see Section 13.14.1). 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.