Nikolaos
Dergiades and
Dimitris M. Christodoulou, The two incenters
of an arbitrary convex quadrilateral,
Forum Geometricorum, 17
(2017) 245--254.
Abstract. For an arbitrary convex quadrilateral ABCD with area A and perimeter
p, we define two points I_1, I_2 on its Newton line that serve as incenters. These points are the centers of two circles with
radii r_1, r_2 that are tangent to opposite sides of ABCD. We then prove that A
= pr/2, where r is the harmonic mean of r_1 and r_2.
We also investigate the special cases with I_1 equiv I_2 and/or
r_1=r_2.
[ps file] [pdf]
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