See Section 24.13.4 for angle measures in two-dimensional geometry.
The angle command finds the measures of angles in space. It can take its arguments in three different ways.
angle(point(0,0,0),point(1,0,0),point(0,0,1)) |
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angle(line([0,0,0],[1,1,0]),line([0,0,0],[1,1,1])) |
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angle(line([0,0,0],[1,1,0]),plane(x+y+z=0)) |
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