180 ∘ = − ( 2 ⋅ 2 ⋅ 5 ⋅ 3 3 ) 1 ⋅ π 2 ⋅ 2 ⋅ 5 ⋅ 3 ⋅ 3 = π {\displaystyle {180^{\circ }}={\frac {-({\cancel {2}}\cdot {\cancel {2}}\cdot {\cancel {5}}\cdot {\cancel {3}}{\cancel {3}})}{1}}\cdot {\frac {\pi }{{\cancel {2}}\cdot {\cancel {2}}\cdot {\cancel {5}}\cdot {\cancel {3}}\cdot 3}}={\pi }}
