# Talk:Pseudotriangle

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Field:  Geometry

Good article. Surprised coverage didn't come until now though. --- ÅñôñÿMôús Dîššíd3nt 20:44, 17 April 2007 (UTC)

These triangles use concave sets. Something doesn't seem right. Alphachimera 01:05, 18 April 2007 (UTC)

## Confusing sentence

The section "Pseudotriangles" says:

The convex hull of any pseudotriangle is a triangle. Each of the three convex vertices is connected by a boundary curve that either lies within the triangle or coincides with one of its edges.

I can't tell what this last sentence is intended to mean. If a "boundary curve" is a path along the boundary of the pseudotriangle, then it should refer to a connecting curve that is entirely on one or more curves connecting vertices, which in the case of a polygon just lies on a sequence of one or more edges. But this would be a vacuous statement. The part about "lies within the triangle" (written so as to contrast with being on an edge) is also vacuous since by definition the pseudotriangle is simply connected.

So I'm removing the sentence. Feel free to reinstate a clarified version. Loraof (talk) 19:48, 28 October 2015 (UTC)

It is not vacuous. If you choose three random vertices of a convex polygon, the boundary curves between them all lie outside the polygon. If you choose the three convex vertices of a pseudotriangle, the boundary curves between them all lie inside the polygon. Note that a sequence of edges and vertices is an example of a curve; there is nothing in the definition of curves that prevents them from passing through vertices. (The word "smooth" is not used here.) —David Eppstein (talk) 20:21, 28 October 2015 (UTC)