IMO Shortlist 1982 problem 17
Dodao/la: arhiva2. travnja 2012.
The right triangles
are similar and have opposite orientation. The right angles are at
, and we also have
be the point of intersection of the lines
. Prove that if the lines
exist, they are perpendicular.
Izvor: Međunarodna matematička olimpijada, shortlist 1982