Ans: (a) $60^\circ$ (b) $21$ (c) $63$
-
$\begin{array}{cl}
& \angle POQ \\
= & 140^\circ – 80^\circ \\
= & 60^\circ
\end{array}$ - Since $OP=OQ=r$ and $\angle POQ=60^\circ$, $\Delta OPQ$ is an equilateral triangle.
$\therefore OP = OQ = PQ$.
Hence, $r=21$.
- The perimeter of $\Delta OPQ$
$\begin{array}{cl}
= & 3 \times PQ \\
= & 3 \times 21 \\
= & 63
\end{array}$
