solving ODE of simple pendulum

Objective: `(d^2θ)/(dt^2)+(b/m)*(dθ)/(dt)+(g/l)*sinθ=0` The above ODE gives the motion of a simple pendulum. The second order ODE has to be convertedinto two first order ODE. consider θ= θ1 `(dθ)/(dt)=(dθ1)/(dt)=θ2` `(d^2θ)/(dt^2)=(d^2θ1)/(dt^2)=(dθ2)/(dt)`…