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| | Body |
 | | Show that the hyperbolic geodesics in the upper half plane are transformed by this inversion into circular arcs (or line segments) perpendicular to the boundary of the disk. |
 | | In particular, consider the plane determined by X and the North and South Poles, the plane tangent to the sphere at X, and the planes tangent to the sphere at the North and South Poles. |
 | | Note that only the lower open hemisphere is projected onto the plane; that is, if X is a point in the lower open hemisphere, then its gnomic projection is the point, g(X), where the ray from the center through X intersects the plane. |
| www.math.cornell.edu /~dwh/books/eg99/Ch16/Ch16.html (1497 words) |
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