Le mercredi 3 juillet 2013 01:07:35 UTC+2, rjf a écrit : > > > > Your statement then translates to RPBSRPN(x^2) = abs(x) . > But then if it ir R+-->R+, the abs() is unnecessary, and RPBSRPN(x^2) = > x. > > No, the abs is necessary: consider the following function: f : R --> R+, x |--> RPBSRPN(x^2) then, for x<0, f(x) = abs(x) = -x.
Surely you don't believe that sqrt of positive numbers are always > positive. > > Yes I do: although a positive number has two square roots, a positive one and a negative one, the standard expectation regarding the sqrt function is that sqrt(x) is THE positive square root of x if x is a positive number. Hence my initial post in this thread. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/groups/opt_out.
