Abstract
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 . We note that the quantities in the formula are naturally dual to each other in , and we give a new dual formula.
Citation
Abigail Thompson. "Invariants of curves in $RP^2$ and $R^2$." Algebr. Geom. Topol. 6 (5) 2175 - 2186, 2006. https://doi.org/10.2140/agt.2006.6.2175
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