1 The diagram shows a sector of a circle of radius 5 cm and angle \(\theta\) radians.
\includegraphics[max width=\textwidth, alt={}, center]{f066f68a-e739-4da3-8ec1-e221461146b0-2_327_358_571_842}
The area of the sector is \(8.1 \mathrm {~cm} ^ { 2 }\).
- Show that \(\theta = 0.648\).
- Find the perimeter of the sector.