Math Forum

Classfying quadrilaterals

I have not completely followed the discussions about quadrilaterals and their
symmetry so I apologize if I raise an issue that has already been

Thanks to William Webber, I stand corrected about my earlier assertion
about quadrilaterals and tesselations.

I guess I can modify the

Yes, at least for convex quadrilaterals, it is true that if there
is one bisector segment which bisects the quadrilateral, then

Ah yes, I see it IS all quadrilaterals (for which the segments
joining the midpoints of pairs of opposite sides meet) - for the
midpoint of

Jim King remarks that in a trapezoid with AB || CD, the segment
connecting the midpoints of AB and CD bisects that containing
the midpoints of

You say "the answers do not include generic quadrilaterals". But
indeed the generic quadrilateral DOES tessellate the

In article <9412211609.AA06198@broccoli.princeton.edu>, conway@math.Princeton.EDU (John Conway) writes:
|> I'm not quite sure why you

I hold no brief for general trapezoids, but here are a couple of
theorems.

Let ABCD be a trapezoid with AB || CD.

The two

On 21 Dec 1994, Chenteh Kenneth Fan wrote:

>
> But I at least offer these:
>
> 1. Which

There appear to be a number of 'computational geometry' algorithms
that involve splitting larger polygons up into (convex) trapezoids
and