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Replies: 1   Last Post: Jan 17, 2013 1:32 PM

 Steven Lord Posts: 18,038 Registered: 12/7/04
Posted: Jan 17, 2013 1:32 PM

news:kd92ed\$mnf\$1@newscl01ah.mathworks.com...
> Hello,
>
> I have this equation: f:= a*x^2 + b
>
> how can i derivate this with rapport to the time just around x using a and
> b as constants.

Unless you've specified that x is a function of t, f is constant with
respect to t and so the derivative WRT time should be 0.

> this is what i want to obtain:
>
> f:=2*a*x*x'
> is there a way to desine a as a constant so the program will not derivate
> it also?

If you're doing this with Symbolic Math Toolbox:

http://www.mathworks.com/help/symbolic/creating-symbolic-variables-and-expressions.html#bs_tekf-1

I'm not sure of the exact syntax to do the equivalent in MuPAD.

--
Steve Lord
slord@mathworks.com