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| | Homogenous and inhomogenous coordinates |
 | | So the point whose inhomogeneous coordinate is a number x, rather than ∞, has homogeneous coordinates (x,1), while the point whose inhomogeneous coordinate is ∞, has homogeneous coordinates (1,0). |
 | | We are thinking of the numbers a,b,c,d as being inhomogeneous coordinates of points on a projective line, so we might want to allow one of them to be ∞. |
 | | The easiest way to do this is write them in inhomogeneous coordinates, and then use their first coordinates (the projection on the x-axis) or their second coordinates (the projection on the y-axis). |
| www.math.fau.edu /Richman/Geometry/coords.htm (1180 words) |
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