6.1 Angles and Their Measure/35

$30^{\circ }\cdot {\frac {\pi }{180^{\circ }}}={\frac {{\cancel {2}}\cdot {\cancel {3}}\cdot {\cancel {5}}}{1}}\cdot {\frac {\pi }{{\cancel {2}}\cdot {2}\cdot {\cancel {5}}\cdot {\cancel {3}}\cdot 3}}={\frac {\pi }{6}}$

${\frac {-5pi}{4}}\cdot {1}={\frac {-5pi}{4}}\cdot {\frac {180}{\pi }}=-225{\circ }$