Solving a nonlinear ODE 2. Order including a trigonometric function of the last order

I have a nonlinear-ODE of the second order with trigonometric functions such that I cannot formulate it depending of the second derivation. For example:

ay'' + b arctan(y'') + cy' + dy=0
y'(0)=0, y''(0)=0

Without existence of a term like arctan(y'') I could write my ode function like

    function output=myodefunc(x,t){
      y(1)=x(2);
      y(2)=(-c*x(2)-d*x(1))/m;
      output=y';
    }

Unfortunately the nonlinear term of the second order (=> b*arctan(y'') ) makes me unable to write the ode in dependence of y'' .

Is there any way to solve such a trigonometric ode numerically (preferred) or symbolically in Matlab?