# forceImage -- declare which is the image of a rational map

## Synopsis

• Usage:
forceImage(Phi,I)
• Inputs:
• Outputs:

## Description

This method allows to inform the system about the image of a given rational map without performing any computation. In particular, this can be used to declare that a rational map is dominant.

 i1 : P6 = QQ[t_0..t_6]; X = minors(3,matrix{{t_0..t_4},{t_1..t_5},{t_2..t_6}}); o2 : Ideal of P6 i3 : Phi = rationalMap(X,Dominant=>2); o3 : RationalMap (cubic rational map from PP^6 to 6-dimensional subvariety of PP^9) i4 : time forceImage(Phi,ideal 0_(target Phi)) -- used 0.000975322 seconds i5 : Phi; o5 : RationalMap (cubic dominant rational map from PP^6 to 6-dimensional subvariety of PP^9)

## Caveat

If the declaration is false, nonsensical answers may result.