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Desargues'
theorem (3D) |
笛沙格定理:笛沙格
（Desargues）定理說明：在射影空間中，有六點A,B,C,a,b,c。Aa,Bb,Cc共點若且唯若AB∩ab,
BC&
cap;bc,CA∩ca共線。 |
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Monge's
theorem (3D) |
Monge's theorem:
In geometry, Monge's theorem, named after Gaspard Monge, states that
for any three circles in a plane, none of which is inside one of the
others, the intersection points of each of the three pairs of external
tangent lines are collinear.
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