This is my situation, please help me.

Cargando  MathematicalFunctions

Cargando  PDEtools

> with(DEtools);
> restart; m[1] := 1; m[2] := 1; l[1] := 1; l[2] := 1; g := 9.8; w := 1; ec1 := (((1/3)*m[1]+m[2]+w)*l[1]^2+((1/3)*m[2]+w)*l[2]^2+(2*((1/2)*m[2]+w))*l[1]*l[2]*cos(beta(t)))*(diff(alpha(t), t, t))+(((1/3)*m[2]+w)*l[2]^2+((1/2)*m[2]+w)*cos(beta(t)))*(diff(beta(t), t, t))-(2*((1/2)*m[2]+w))*l[1]*l[2]*sin(beta(t))*(diff(alpha(t), t))*(diff(beta(t), t))-((1/2)*m[2...