ProfJP

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7 years, 113 days

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These are replies submitted by ProfJP

Thank you two, Rouben and Tomleslie,
The problem was that I need the values of the unknown variables at equidistant times  stored in some array (A in the ode I wrote in my question). So the solution dsol is some matrix of matrices (or some indexed, I don't know exactly). For that reason (I think), your solution, Rouben, does not work : dsol(1.23) (or even for some date of my A array) is undefined. If I do this, I get some very long error message, that seems to me to be some insult (!). Yours, Tomleslie, works fine. Instead of getting some 5 columns indexed (t,x(t),vx(t),y(t),vy(t)) I get some 7 columns one containing ax(t) and ay(t). But if I don't do exactly what you write, it does'nt work anymore. For instance if I define the dummies before the eqs, or if, instead of defining the dummies, I onely write something like :

Ax:=t->diff(x(t),t,t);Ay:=t->diff(y(t),t,t);

And I don't understande why it does'nt work anymore.

One more time, thank you both.

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