# How to obtain the time period from the Lagrangian equation for a simple pendulum?

Solving the Lagrangian equation for a simple pendulum we get the following equation: $$\ddot{\theta} + \frac{g \theta}{l} = 0,$$ (when $$\theta$$ is small enough). We already know that time period of a simple pendulum is given by $$T= 2π \sqrt{l/g}.$$ But how can we derive the time period $$T$$ from the equation that is obtained from the Lagrangian equation?

$$\frac{d^2 \theta}{dt^2}=-g\frac{\theta}{l}$$
From the analogies you can just say that the time period would be $$2\pi\sqrt{\frac{l}{g}}$$