O7:    Positive numbers have positive reciprocals.

"If  a>0  then  1/a>0."  (see ita-2-2-13-pg20)

"In fact  a·(1/a) = 1>0,  [and by O5 both factors in the product must be positive since one factor and the product are positive]."  (see ita-2-2-13-pg20)

Recall that division, and hence 1/a,  was defined in F4.  Also,  1/a  is called the reciprocal of a.


Converted [ in part ] by Mathematica      December 4, 2007