Pendulum. Find the frequency of oscillation of a pendulum of length $L($Fig$,42),$ neglecting air resistance and the weight of the rod, and assuming $$ to be so small that $sin$ practically equals $.$

In addition, solve for the constants A and $B$ in the general solution when $=0\mathrm{.}1$ and ${}^{\text{'}}=0$ at $t=0.$