Learning Guide Learning Guide

168 • Chapter 5: Evaluation and SimplificationThe assuming CommandTo perform a single evaluation under assumptions on the name(s) in anexpression, use the assuming command. Its use is equivalent to imposingassumptions by using the assume facility, evaluating the expression, thenremoving the assumptions from the expression and names. This facilitatesexperimenting with the evaluation of an expression under differentassumptions.> about(a);a:nothing known about this object> sqrt(a^2) assuming a about(a);a:nothing known about this object> sqrt(a^2) assuming a>0;aYou can evaluate an expression under an assumption on all names inan expression> sqrt((a*b)^2) assuming positive;a b~or assumption(s) on specific names.> ln(exp(x)) + ln(exp(y)) assuming x::real, y::complex;x~ + ln(e y )