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IsInImage    --    check if a RINGELEM is in image of RINGHOM


Syntax 
IsInImage(phi: RINGHOM, f: RINGELEM): BOOL

Description
This function checks if f is in the image of phi (better use preimage0 directly).

Example 
/**/  QQxyz ::= QQ[x,y,z];
/**/  QQab  ::= QQ[a,b];

/**/  use QQab;
/**/  phi := PolyAlgebraHom(QQxyz, QQab, [a+1, a*b+3, b^2]);

/**/  IsInImage(phi, b);
false
/**/  preimage0(phi, b);
0

See Also