Re: Displaying Equations Symbolically and Numerically

*To*: mathgroup at smc.vnet.net*Subject*: [mg114757] Re: Displaying Equations Symbolically and Numerically*From*: David Bailey <dave at removedbailey.co.uk>*Date*: Thu, 16 Dec 2010 05:47:49 -0500 (EST)*References*: <ieadkv$r9h$1@smc.vnet.net>

On 15/12/10 12:51, Gregory Lypny wrote: > Hello everyone, > > I would like to be able to display equations for my students in symbolic > form on the left side and with the numbers plugged in on the right side > but am not quite sure how to do it programmatically. Suppose my > equation in "symbolic" form is > > sqrt(x^(a+b)) + c ln(d/e) > > I know I can make it look like real math by having it displayed as > TraditionalForm. However, I also want to display the solution with > particular values for the variable x and the parameters a, b, c, d, and > e slotted in, something like > > sqrt(x^(a+b)) + c ln(d/e) = sqrt(9^(2+1)) + 4 ln(32/8) = answer > > to recognize that some students may be a little rusty at simplifying on > the fly. Wrapping the whole package in Manipulate would put the icing > on the cake. > > Any tips on how apply the appropriate styles would be most appreciated. > > Regards, > > Gregory > > > Your question is a little vague (I don't see where Manipulate might come in), but presumably it is the middle expression that you have difficulty with - because it is partially evaluated. The easiest way to obtain it, is to perform the substitutions on the expression wrapped in HoldForm. HoldForm[sqrt (x^(a + b)) + c ln (d/e)] /. {9 -> 9, a -> 2, b -> 1, c -> 4, d -> 32, e -> 8} You can then remove the HoldForm, with for example expr/.HoldForm->Identity The general problem of making Mathematica follow the steps that a person might have used in a hand calculation, is much more difficult, however. Mathematica often uses quite exotic methods to solve (for example) integrals, and anyway these intermediate steps are not displayed. David Bailey http://www.dbaileyconsultancy.co.uk