π 2 ⋅ 180 ∘ π = 2 ⋅ 2 ⋅ 3 ⋅ 3 ⋅ 3 π = 90 ∘ {\displaystyle {\frac {\pi }{\cancel {2}}}\cdot {\frac {180^{\circ }}{\pi }}={\frac {{\cancel {2}}\cdot {2}\cdot {3}\cdot {3}\cdot {3}}{\pi }}=90^{\circ }}
