In the course of deriving the formula $T=2\pi\sqrt{L/g}$ for the period of a pendulum of length $L$, one obtains the equation $a_{T}=-g\sin{\theta}$ for the tangential acceleration of the bob of the pendulum.
For small angles, find the linear approximation at 0 for $\sin{x}$, thereby giving us one for $a_{T}$.

$\sin{x}\thickapprox$