FullSimplify Question

*To*: mathgroup at smc.vnet.net*Subject*: [mg48586] FullSimplify Question*From*: "Dana DeLouis" <delouis at bellsouth.net>*Date*: Sat, 5 Jun 2004 19:58:07 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Hello. Hate to ask, but does anyone know what the issue is in the following? This equation basically is 5 when t is less than 0, and 1 when t>=0 equ = 5 - 4*UnitStep[t] If I ask to "Simplify" this, by using the Sign function, I get the following, which is not even close FullSimplify[equ, TransformationFunctions -> {Sign}] 1 - UnitStep[t] The above is 1 when t<0, and 0 when t>=0. I have to use both functions "FourierTransform" and "InverseFourierTransform" to get the correct form. 3 - 2*Sign[t] My question is that I can't figure out why FullSimplify was so far off. Would Mathematica have been better to leave the expression unevaluated so as to use other methods? When the equation is more complicated, it may be harder to spot such "errors." Thanks for any insight. Dana DeLouis delouis at bellsouth.net