In addition to John Randall's reference to

http://en.wikipedia.org/wiki/Real_number#Generalizations_and_extensions

there is a comment by Walter Rudin, Arithmetic in [0,infinity],
Section 1.22 of his Real and Complex Analysis, Third Edition:

"It may seem strange to define 0*infinity = 0.  However, one verifies 
without difficulty that with this definition the commutative, 
associative, and distributive laws hold in [0,infinity] without any 
restriction.

"The cancellation laws have to be treated with some care ..."

Sorry, Henry.  I'm getting as far away from _. as I can!

Kip Murray

[EMAIL PROTECTED]
http://www.math.uh.edu/~km
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