In most Olympiad problems, part of the proof relies on showing the equality of two angles that seemingly have no connection with each other. Often, these require you to write a list of equalities involving various angles, and so the name "angle chasing". One popular technique which involves the concept of anti-parallel lines, is the theorem of Reim.
The All-Pakistan National Mathematics Olympiad is due to be held on Saturday, the 3rd of November this year. It is the elite mathematics competition of Pakistan, and ultimately a part of the selection process for the International Mathematical Olympiad (IMO), and the Asian Pacific Mathematics Olympiad (APMO).
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