Re: How to get sqrt(Year^2)===Year?

*To*: mathgroup at smc.vnet.net*Subject*: [mg75796] Re: How to get sqrt(Year^2)===Year?*From*: dh <dh at metrohm.ch>*Date*: Thu, 10 May 2007 05:27:24 -0400 (EDT)*References*: <f1s1v4$fip$1@smc.vnet.net>

Hi, a square root has actually two values but by choosing a branch cut, the function is made unique. Therefore, the Sqrt of a real number is by definition positive. Therefore, Sqrt[x^2] is not equal to x if x<0. However, if you tell Mathematica that Year is positive you will get what you want. E.g. Simplify[x==Sqrt[x^2],x>0] hope this helps, Daniel Hatto von Aquitanien wrote: > If I have some expression which takes the square root of a square, it > evaluates leaving the whole square root expression unchanged. > > Year == (Year^2)^(1/2) > > just returns what I entered when evaluated. > > Year == Year > > evaluates to True. > > How do I persuade Mathematica to evaluate the first expression completely?