Department of Mathematics
Invariants of curves in RP^2 and R^2
- Author(s): Thompson, Abigail
- et al.
Published Web Locationhttps://arxiv.org/pdf/math/0602003.pdf
There is an elegant relation found by Fabricius-Bjerre [Math. Scand 40 (1977) 20--24] among the double tangent lines, crossings, inflections points, and cusps of a singular curve in the plane. We give a new generalization to singular curves in RP^2. We note that the quantities in the formula are naturally dual to each other in RP^2, and we give a new dual formula.