Discussion:  All Topics in Geometry 
Topic:  Is a rhombus a kite? 
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Subject:  RE: Is a rhombus a kite? 
Author:  patb 
Date:  Apr 21 2008 
about "kites" but rather "deltoids" and a deltoid by definition is a
quadrilateral with two pairs of congruent adjacent sides (whether or not
distinct depends on the book...).
My question: Does the "standard" definition of quadrilateral assume
convexness?

I think in many high school geometry textbooks they will make some statement
early in the book that all polygons are to be assumed convex unless otherwise
stated...
I think this is a mistake, but I'm not sure I have convinced anyone to change
this approach.
As for the name of the "concave kite" I have referred to it as a dart and
arrowhead.
In the link I posted previously, I note that Proclus calls the dart shape a
foursided triangle, and other ancients called it a "barb" or a
"hollowangle". Unfortunatly I did not make a note of where I picked up that
delicious bit of information, so use with caution.
Pat
 
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