$AOB$ is a sector of a circle with center $ O$ and radius $OA = 10$.
Circle with radius $3$ is inscribed in this sector such that it touches radius $OA$, radius $OB$ and arc $AB$.
Find the length of the chord $AB$.
I don't know where to begin. To calculate the length of $AB$ ,
we'll need the length of perpendicular from $O$ to $AB$.
( then we can use pythagoras theorem to get half of $AB$ and then $AB$) .
But how can I find that?