Lean-Workbook Plus 43176: Trigonometric identity

For every $m\in[-1,1]$, there is $\theta\in[-\pi/2,\pi/2]$ such that $m=\sin\theta$.

Source: Lean-Workbook row lean_workbook_plus_43176 (Apache-2.0). The unchanged proposition comes from the original record; its missing mathematical imports and namespaces are restored here.