In the picture all of the red segments are of equal length and all of their endpoints lie on one of the two blue lines. Determine all possible values for the smaller angle between the blue lines.

(This problem is a special case of a problem discovered by Daniel Shapiro, professor of mathematics at Ohio State University. His problem generalizes a problem he saw years ago.)

Is Eric's proof longer because it is more elementary, or is Bractal's proof shorter because more details are left to the reader?  Whatever, both proofs show the tenacity of a pit bull.  Can't say that about my proof.  I got a monster hint from Shapiro.

Posted by McWorter on 2005-06-09 23:02:30