Coordinate system transformations to add information?
Specific proof outline
Matrix we found Monday provides
the canonical-to-instance transformation, but isn’t
invertible
Try to fill in the 3rd column so the determinant is non-0
Constraints associated with requiring the instance triangle
to really be a triangle, rather than degenerating to a point
or line segment, ensure that at least 1 of the cross-product
terms in the determinant is non-0
So pick a, b, and c coefficients to give non-negative
products with their cross-product terms, e.g., based on
signs of cross products, and the resulting determinant has
to be positive, i.e., non-0
Fleshing this out with background literature, implementation,
etc. could be an at-least-minimally publishable (e.g., at
GREAT Day) course project