6.1 Angles and Their Measure/51

${\frac {180^{\circ }}{\pi }}\cdot {\frac {\pi }{\cancel {2}}}={\frac {{\cancel {2}}\cdot {2}\cdot {3}\cdot {3}\cdot {3}}{\pi }}=90^{\circ }$ \frac{\pi}{\cancel{2}} \frac{180^{\circ}}{\pi}