for n being Nat for RAS being ReperAlgebra of n for a, b being Point of RAS for p being Tuple of (n + 1),RAS for W being ATLAS of RAS for v being Vector of W for x being Tuple of (n + 1),W st (a,x) . W = p & (a,v) . W = b & *' (a,p) = b holds Phi x = v