− π 2 {\displaystyle {\frac {-{\cancel {\pi }}}{\cancel {2}}}} ⋅ {\displaystyle \cdot } 2 ⋅ 2 ⋅ 5 ⋅ 3 ⋅ 3 π = − 90 ∘ {\displaystyle {\frac {{\cancel {2}}\cdot 2\cdot 5\cdot 3\cdot 3}{\cancel {\pi }}}=-90^{\circ }}
