Solution

Convert to radians: $20^{\circ}, 30^{\circ}, -60^{\circ}$


  • $\displaystyle{20^{\circ} = 20 \left( \frac{\pi}{180} \right) \textrm{ radians } = \frac{\pi}{9} \textrm{ radians}}$

  • $\displaystyle{30^{\circ} = 30 \left( \frac{\pi}{180} \right) \textrm{ radians } = \frac{\pi}{6} \textrm{ radians}}$

  • $\displaystyle{-60^{\circ} = -60 \left( \frac{\pi}{180} \right) \textrm{ radians } = -\frac{\pi}{3} \textrm{ radians}}$