COURSE OF PROJECTIVE GEOMETRY


§ 21:


O81
Find a 2 by 2 matrix whose determinant is to be 0.
We get x' y' = z' (ρ z' - τ x').


O82
By substitution of the coordinates of the five points in the equation we get five linear equations with six unknown variables aij. In general, this gives a 1-dimensional solution space, so the coefficients aij are then unique up to a scalar factor.
(These five linear equations are linearly independent if and only if the five points are freely situated.)


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