[挑戰]正三角形內切兩圓 8 12 月,2009 ginwhaLeave a comment [挑戰]正三角形內切兩圓 ΔABC is equilateral with side length 4. D is a point on BC such that BD = 1. If r and s are the radii of the inscribed circles of ΔADB and ΔADC respectively, find rs. link