
Three points, A, B and C.
angle returns the measure of the undirected angle
BAC.
Input:
angle(point(0,0,0),point(1,0,0),point(0,0,1))
Output:
pi/4
 Two intersecting lines.
angle returns the measure of the angle between the lines.
Input:
angle(line([0,0,0],[1,1,0]),line([0,0,0],[1,1,1]))
Output:
acos((sqrt(6))/3)
 A line and a plane.
angle returns the measure of the angle between the line and
the plane.
Input:
angle(line([0,0,0],[1,1,0]),plane(x+y+z=0))
Output:
acos((sqrt(6))/3)