Lean-Workbook Plus 17727: Trigonometric identity

The complementary-angle identity gives $\sin36^\circ=\cos54^\circ$. The Lean statement uses the radian arguments $36\pi/180$ and $54\pi/180$.

Source: Lean-Workbook row lean_workbook_plus_17727 (Apache-2.0). The unchanged proposition comes from the original record; its missing mathematical imports and namespaces are restored here.