Search found 183 matches
- Thu Aug 15, 2013 12:47 pm
- Forum: International Mathematical Olympiad (IMO)
- Topic: IMO 2013, Day 2-P4
- Replies: 2
- Views: 2131
Let $AH$ meets $BC$ at $L$. So $AL\perp BC$ Let $W$ lies between $L$ and $C$ We have $\measuredangle XBW=\measuredangle XNW=90$. So $\measuredangle XNB=\measuredangle =90-\measuredangle BNW=\measuredangle CNW$ $\measuredangle XBN=90-\measuredangle B=\measuredangle NCW$ So $\triangle XBN$ and $\trian...
The quadrilateral $ABCD$ is inscribed in a circle.The lines $AB$ and $CD$ meet at $E$,The diagonals meet at $F$.The circumcircle of $AFD$ and $BFC$ meet again at $H$.Prove that $\angle EHF$ is a right angle.