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# Matlab Symbolic tool: Integration

## Matlab Symbolic tool: Integration

(OP)
hi guys,

I'm trying to calculate a complex integral of a function V(x,y,z) but the integral is wrt time. The symbolic variables x, y and z are also time dependent. I started with a simple case to try to learn how to do it. Let's say V = sin(x) and I want to calculate the integral wrt time. Do I need to create another symbolic variable Xdot that symbolize dx/dt or something like this. If so How would I do that.
Any wisdom out there to help me out, please!!

Munir

### RE: Matlab Symbolic tool: Integration

Do you even have the Symbolic Math Toolbox?

Have you read the help files?

### RE: Matlab Symbolic tool: Integration

What extra symbol? 'diff' works fine....
And yes, I also suggest you read the help files.

Fe

### RE: Matlab Symbolic tool: Integration

» syms v x b t
» x=exp(-b*t)

x = exp(-b*t)

» v=sin(x)

v = sin(exp(-b*t))

» int(v,t)

ans = -sinint(exp(-b*t))/b

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### RE: Matlab Symbolic tool: Integration

Whoops.  What the heck is sinint? Should've been cos.

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### RE: Matlab Symbolic tool: Integration

I see sinint was defined in the help. Maybe the answer is correct.

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### RE: Matlab Symbolic tool: Integration

At first glance it looked like an easy integral.  It would be easy to find derivative of v(x(t)) with chain rule, but not so easy to find the integral.  Matlab is probably right.

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