6.1 Angles and Their Measure/41

${180^{\circ }}={\frac {-({\cancel {2}}\cdot {\cancel {2}}\cdot {\cancel {5}}\cdot {\cancel {3}})}{1}}\cdot {\frac {\pi }{{\cancel {2}}\cdot {\cancel {2}}\cdot {\cancel {5}}\cdot {\cancel {3}}\cdot 3}}=-{\frac {\pi }{3}}$