Answer 1

We have: 
\[\pi \text{ rad }= 180^\circ\]
\[ \therefore 1 \text{ rad }= \left( \frac{180}{\pi} \right)^\circ \]
\[ \left( \frac{18\pi}{5} \right)^c = \left( \frac{180}{\pi} \times \frac{18\pi}{5} \right)^\circ \]
\[ = \left( 36 \times 18 \right)^\circ\]
\[ = {648}^\circ\]