Re: Derivatives

*To*: mathgroup at smc.vnet.net*Subject*: [mg113742] Re: Derivatives*From*: Walking Randomly <michael.p.croucher at googlemail.com>*Date*: Wed, 10 Nov 2010 06:28:02 -0500 (EST)*References*: <ib8csf$2fb$1@smc.vnet.net>

On Nov 8, 8:37 am, will <will.yeu... at gmail.com> wrote: > Hello, > > I am trying to take the derivative (d/dx) of a very messy equation > that is more easily expressed initially as a function of y, then y and > a function of x. Rather than have to substitute and expand, can a set > of equations be input and instructed to find a derivative wrt x? > > (A little bit new to Mathematica) > > Thanks. > Will Hi You can tell Mathematica that y is a function of x by doing y[x]. For example, say we wanted to differentiate x=Sqrt[y] where y is a function of x. You can do this has follows D[x == Sqrt[y[x]], x] Stare at the answer for a bit and you'll see that it gives a result consistent with what we'd get if we took y=x^2 and differentiated. Cheers, Mike www.walkingrandomly.com