



If two
lines are NOT parallel,



they
cross somewhere. 











If you
look close, you can see that where the two lines cross 


they make
four angles ... 











(these
numbers are nothing special, it's just what we use to count the
angles) 


There is
one funny thing that happens with these angles. 


It turns
out that no matter how the lines cross, 


the
angles opposite each other are always the same size. 











Most
people would say: 


"Hey,
that's kind of cute" and go on with their lives. 


Of
course, math people aren't most people. 





They
said: 


"I
bet if we try really hard, 


we can
build a whole bunch of math around this." 





copyright 2005 Bruce Kirkpatrick 
