@Joe Riel

I was not able to use Ctrl-Shift-", it might be be because I'm on a MAC. I tried Command-Shift-" to but that din't work either.

@cismicstring

It now see what you mean, i have simplified the ode system to:

spring_ODE_setup.mw

However it sill dosn't work, but now it just don't evaluate it simply skip it.

Thank you both. Since i use Math 2D I like Markiyans way. I also ended up createing this procedure to solve my problem: 

> trigSolve := proc (eq, na) local sol, memory, restore, elems, i; sol := [solve([eq, 0

> trigSolve(4*cos(t)+2*cos(2*t) = 0, t) # {t = arccos((1/2)*sqrt(3)-1/2)}, {t = 2*Pi-arccos((1/2)*sqrt(3)-1/2)}

solve_proc.mw

I hope someone else will find it usefull, and perhaps post an improvement.