Date: Sun, 9 Feb 1997 09:07:57 -0700
From: Rich Morrow
Subject: The nine dots problem
These comments are in regard to your nine dots puzzle. If the dots are not infinitesimally small mathematical points, they can be connected with three lines. Slant one line downwards through the top three points, i.e. go through the top part of the top left dot, through the center of the top middle dot, and through the lower part of the right top dot. Draw a similar line through the dots in the bottom row. For the middle row, draw a similar line that has an opposite slope. The three lines will intersect.
If you allow changes in the surface on which they are drawn, it is possible to draw a single line through all nine dots. If you want to try to figure out how to fold the paper to get all nine in a line, put each row of three dots close together and the three rows far apart.
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