plangeo4
http://www.openmath.org/cd
http://www.openmath.org/cd/plangeo4.ocd
2006-06-01
experimental
2004-06-01
0
5
This CD defines symbols for planar Euclidean geometry. In particular, it is concerned with projective and affine coordinates of points and lines.
set_coordinates
This symbol defines the coordinates of a point or a line. The coordinates are the projective coordinates and consist of a vector of length 3. Points whose third coordinates are zero are the points at infinity. The line whose first two coordinates are zero is the line at infinity.
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coordinates
This function yields the coordinates vector if applied to a point or line with coordinates.
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To extract the coordinates of a point A with coordinates (1,2,3):
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is_affine
Boolean function testing whether a point or line is affine.
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affine_coordinates
This function yields the affine coordinates vector if applied to a point or line with coordinates in the affine plane.
The affine coordinates (1/3,2/3) are expressed as follows for the point A with projective coordinates (1,2,3).
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set_affine_coordinates
Defines the affine coordinates of an affine point or line.
Assign the affine coordinates (1/3,2/3) to A.
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