Online Geometry Problem 715: Triangle, Altitudes, Parallel, Circumcircle,
Angle, Measurement.
Level: High School, Honors Geometry, College,
Mathematics Education

The figure shows a triangle ABC with the
altitudes AA', BB' and CC'. The measure of angle BAC is 59 degrees. L is
a line through A' parallel to B'C'. L meets AB extended and AC at D and
E, respectively. B'C' and CB meet at F. The circumcircle of triangle DEF
meets BC at H. Find the measure of angle B'HC'.