2001 IMO Shortlist Problems/G2
Problem
Consider an acute-angled triangle . Let be the foot of the altitude of triangle issuing from the vertex , and let be the circumcenter of triangle . Assume that . Prove that .
Solution
See 2001 IMO 1 page. https://artofproblemsolving.com/wiki/index.php/2001_IMO_Problems/Problem_1