The two incenters of an arbitrary convex quadrilateral - Nikolaos Dergiades and Dimitri M. Christodoulou 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. ✪ ✪ ✪ ✪ ✪ Link tải tài liệu: LINK TẢI TÀI LIỆU Theo LTTK Education