How to take a derivative of x with respect to time.

Hello.

I'm trying to solve some derivatives in matlab for my dynamic course.

The problem is im a total noob to this program and i was wondering of some of you could help me out with this probaly simple problem.

I would like to get the time derivative of x with respect to t (time) but x^2 is a chain rule and xy would be a product rule.

Ive tried to solve it myself in the code below, its probaly totally wrong with my horrible coding skills.

Thanks.

syms x(t) y(t) z(t)
% f = [2*x-3*x*y+y^2-x*z+y*z^2-4*x*y*z , -x^2+x*y^2-2*y+5*y*z-x*z^2]
o = 2*x-3*x*y+y^2-x*z+y*z^2-4*x*y*z
p = -x^2+x*y^2-2*y+5*y*z-x*z^2

H = diff(x,t)*y*z+x*diff(y,t)*(z)+x*y*diff(z,t)

[madhan ravi]

Could you elaborate more? What problem are you having ? Illustrate with an expected result.

[Henrik Kristiansen]

o should end up being equal to 2ẋ-3(ẋy+xẏ)+2yẏ-(ẋz+xż)+ẏz^2+2yzż

All the dotted letters are the time derivatives.

im having problems making matlab do the time derivatives with respect to x but x is a function

[Henrik Kristiansen]

dx^2/dx * dx/dt = 2xẋ

Answer 1

[Koushik Vemula]

According to what I understand, you are trying to get the differentiation of variable ‘o’ with respect to the parameter ‘t’.

For this we have a function ‘diff’ in MATLAB which comes under ‘syms’ module, it can be used in the following manner

diff(o, t) 

This will give you the expected answer.

Refer this documentation for more understanding of the function ‘diff’ : https://www.mathworks.com/help/symbolic/diff.html

[Henrik Kristiansen]

Thanks, ill try that :)