Finding time derivatives in terms of other variables

[thecoop]

Hi guys

I have 5 term which each term includes three function of time (autonomous system ), i want to obtain time derivative of each term as other terms for example if i define each term as a dimensionless variable , e.g. x , y , z , v , w , i want to know dx/dt = as a combination of x , y , z , v , w.


In maple or mathematica or MATLAB is there any way to do it ?



thx

 

[Pythagorean]

in MATLAB it requires the symbolic toolbox (which you have to pay extra for). I'm pretty sure mathematica comes automatically with symbolic math functions. No idea about maple.

 

[Pythagorean]

try typing this:

(d/dt)t^2

into here:

http://www.wolframalpha.com/

for a taste of mathematica

 

[NemoReally]

Mathcad also has symbolic differentiation and can do numeric differentiation if that would be better suited to your purpose.
Can you give an example of a couple of your terms?

 

[thecoop]

Mathcad also has symbolic differentiation and can do numeric differentiation if that would be better suited to your purpose.
Can you give an example of a couple of your terms?

1=ρ/3 H^2+x1+x2+x3+x4+x5

x1=ρ λ f/6 H^2
x2=-ρ λ f' R/6 H^2
x3=λ f" ρ R`/H
x4=3 λ f' ρ
x5=ρ^2 λ f' / 3 H^2

where H=a`(t) /a(t)

R=6(2H^2+H`)

f(R)

ρ(t)

λ Constant
f' = the first derivative wrt R
f"= the second derivative wrt R
R`=the first derivative wrt t
a`=the first derivative wrt t


I want each term derivation wrt to time expressed as other terms(x1 , x2 , ...) or at least have a Coefficient as R and f ( with its derivations wrt to R ) .

 

[thecoop]

try typing this:

(d/dt)t^2

into here:

http://www.wolframalpha.com/

for a taste of mathematica

i don't know with what command i can do this !