       Re: Can Mathematica Do This?

• To: mathgroup at smc.vnet.net
• Subject: [mg8181] Re: Can Mathematica Do This?
• Date: Mon, 18 Aug 1997 03:07:05 -0400
• Organization: Univ. of Pittsburgh Computer Science
• Sender: owner-wri-mathgroup at wolfram.com

```Fahad A Hoymany (fahad at cs.pitt.edu) wrote:
:      Before I go on to investigate this problem, and because I'm not
: familiar with the capability of Mathematica, could someone tell me if
: Mathematica can:

: 1) Find the partial derivative of a function of three variables, f(x,y,z),
:    with respect to each variable?
: 2) Find the minimum (x,y,z) for f?

:    The function f is not very complicated, involving only first and second
: order expressions in x,y, and z.

:    I'd very much appreciate a "yes" or "no" answer.

Thanks to those who e-mailed me with some suggestions.  Although, I am
now a little more familiar with Mathematica, the problem I need to solve
seems to be too tough for Mathematica, even though it "looks" like a simple
problem.  I tried FindMinimum, NDsolve, among other attempts, and I either
get an error of the form ".... something is not a real number", or
Mathematica takes the command but never returns an answer!  Here is the
problem in case some kind soul wants to give it a try:

Find the minimum of f in c and h
f = (c d1+d2) r (2/((c+1) (h-c+1))) + d3 h/2 +
(c d4+d5) r (2/((c+2)*(h-c+1)))

Note that c <= h, and c,h >=0.  If it helps, h < 10,000.  The d's are
real numbers in the range 0 to 1.0, and r is real in the range 0 to
100,000.

Best regards