code: def cos_table() -> dict[int, Callable[[], Expr]]:
      r"""Lazily evaluated table for $\cos \frac{\pi}{n}$ in square roots for
      $n \in \{3, 5, 17, 257, 65537\}$.
  
      Notes
      =====
  
      65537 is the only other known Fermat prime and it is nearly impossible to
      build in the current SymPy due to performance issues.
  
      References
      ==========
  
      https://r-knott.surrey.ac.uk/Fibonacci/simpleTrig.html
      """
      return {3: cos_3, 5: cos_5, 17: cos_17, 257: cos_257}
  
file_path: sympy/sympy/functions/elementary/_trigonometric_special.py
imports: from __future__ import annotations
  from typing import Callable
  from functools import reduce
  from sympy.core.expr import Expr
  from sympy.core.singleton import S
  from sympy.core.intfunc import igcdex
  from sympy.core.numbers import Integer
  from sympy.functions.elementary.miscellaneous import sqrt
  from sympy.core.cache import cacheit
label_desc: Use image node_id 8 for calling a global function with example usage: cos_table() and returns: dict