i1 :  map defined by the quadrics through a rational normal quartic curve
Phi = rationalMap PP_(ZZ/65521)^(1,4);
o1 : MultirationalMap (rational map from PP^4 to PP^5)

i2 :  we see Phi as a dominant map
Phi = rationalMap(Phi,image Phi);
o2 : MultirationalMap (dominant rational map from PP^4 to hypersurface in PP^5)

i3 : time inverse Phi;
 used 0.113075s (cpu); 0.111987s (thread); 0s (gc)
o3 : MultirationalMap (birational map from hypersurface in PP^5 to PP^4)

i4 : Psi = last graph Phi;
o4 : MultirationalMap (birational map from 4dimensional subvariety of PP^4 x PP^5 to hypersurface in PP^5)

i5 : time inverse Psi;
 used 0.400036s (cpu); 0.225622s (thread); 0s (gc)
o5 : MultirationalMap (birational map from hypersurface in PP^5 to 4dimensional subvariety of PP^4 x PP^5)

i6 : Eta = first graph Psi;
o6 : MultirationalMap (birational map from 4dimensional subvariety of PP^4 x PP^5 x PP^5 to 4dimensional subvariety of PP^4 x PP^5)

i7 : time inverse Eta;
 used 0.952081s (cpu); 0.747676s (thread); 0s (gc)
o7 : MultirationalMap (birational map from 4dimensional subvariety of PP^4 x PP^5 to 4dimensional subvariety of PP^4 x PP^5 x PP^5)

i8 : assert(Phi * Phi^1 == 1 and Phi^1 * Phi == 1)

i9 : assert(Psi * Psi^1 == 1 and Psi^1 * Psi == 1)

i10 : assert(Eta * Eta^1 == 1 and Eta^1 * Eta == 1)
