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isTriangular -- Decides whether a polynomial system is triangular



A polynomial system is triangular if, after a monomial change of coordinates, there is a proper subset of $k$ equations which involve only the first $k$ variables. This function checks whether a polynomial system (or set of supports) is triangular.

The function isTriangular accepts a list of polynomials forming a system.

i1 : R=QQ[x,y];
i2 : F={3+x^2*y^2-(17/3)*x^4*y^4,2-x^2+5*y^2-13*x^2*y^2};
i3 : isTriangular F

o3 = true

The function isTriangular also accepts a list of supports encoded as matrices.

i4 : A = {matrix{{0,2,4},{0,2,4}},matrix{{0,0,2,2},{0,2,0,2}}};
i5 : isTriangular A

o5 = true
i6 : B = {matrix{{0,2,4},{0,2,3}},matrix{{0,1,0},{0,0,1}}};
i7 : isTriangular B

o7 = false

See also

Ways to use isTriangular :

For the programmer

The object isTriangular is a method function.