mr_picky

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These are questions asked by mr_picky

I'm working on simulating a triple pendulum. I have the numeric solution of the ODEs and some nice plots that indicate I'm on the right track. I would to animate these solutions. 
It seems like there is a way to plot the positions over time, as well as the lines between the points. If anyone can put me on the right track towards this, I would really appreciate it. 

I have a set of 3 differential equations called "odesys" that I need to solve. I input this line to solve them and I get the following error. 

sols := dsolve([odesys, ICs], {Theta[1](t), Theta[2](t), Theta[3](t)})
Error, (in dsolve) not a system with respect to the unknowns {Theta[1](t), Theta[2](t), Theta[3](t)}
 

I've also tried it using the exact syntax that the thetas are in the equation and I get this error. 

sols := dsolve([odesys, ICs], {Theta(t)[1], Theta(t)[2], Theta(t)[3]});
Error, (in dsolve) required an indication of the solving variables for the given system
 

I don't know even know which error message is better. The equations are second order and non-linear if that has any bearing on anything. 

To simplify, I will use some of my test code, but I need to use a vector index within a sum. 
m=Vector[column](3, [1, 1, 1]);
sum(L[k], k = 1 .. 3) ;

returns "Error, bad index into Vector" 
is there a way around this problem?

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