Projective Geometry

[Norman.Galois]

I'm doing reading course on Projective Geometry.

I was presented this question (in the textbook, not homework):

In $P_2 R$, let A, B, and C be points on a line L and let A', B', and C' be points on a line L'. Prove there exists points $S_1$, $S_2$ and $S_3$, and lines $l_1$ and $l_2$ such that projection from L to $l_1$ with center $S_1$, ...

And it continues. The remainder is not important. What do they mean by center $S_1$?

Thank you.

 

[radou]

Isn't it a fixed point in some projection?

 

[Norman.Galois]

Isn't it a fixed point in some projection?

That seems to make more sense. I'll try that out. Thanks!