MathDB

2

Part of 2013 Poland - Second Round

Problems(1)

Two circles

Source: 64 Polish MO 2013 Second Round - Problem 2

4/21/2018
Circles o1o_1 and o2o_2 with centers in O1O_1 and O2O_2, respectively, intersect in two different points AA and BB, wherein angle O1AO2O_1AO_2 is obtuse. Line O1BO_1B intersects circle o2o_2 in point C≠BC \neq B. Line O2BO_2B intersects circle o1o_1 in point D≠BD \neq B. Show that point BB is incenter of triangle ACDACD.
geometrycirclesincirclePolandincenter