geometry puzzle

[cellio]

You're being too productive; let me help:

World's hardest easy geometry problem, forwarded by a coworker, allegedly solvable with pure geometry (no trigonometry).

Comments

[cellio]

I briefly wondered whether measuring would be legit (proportionally, not with a scale), but concluded that I am not nearly a good-enough draftman to be able to rely on the results. :-)

[ichur72.livejournal.com]

I cheated and checked my solution against Professor Google ... and D'OH! I'm wrong.