Hi, I would to check if my transformation from an ODE 2nd degree to ODE 1st degree is fine:

X''(t)+X(t)=0

I set:

X1(t)=X(t)

X2(t)=X'(t)

this implies that:

X1'(t)=X2(t)

so the original equation becomes:

X2'(t)=-X1(t)

PLease tell me if I am right?

B