code: def test_euler_pendulum():
      x = Function("x")
      t = Symbol("t")
      L = D(x(t), t) ** 2 / 2 + cos(x(t))
      assert euler(L, x(t), t) == [Eq(-sin(x(t)) - D(x(t), t, t), 0)]
  
file_path: sympy/sympy/calculus/tests/test_euler.py
imports: from sympy.core.function import Derivative, Function
  from sympy.core.relational import Eq
  from sympy.core.symbol import Symbol, symbols
  from sympy.functions.elementary.trigonometric import cos, sin
  from sympy.testing.pytest import raises
  from sympy.calculus.euler import euler_equations
label_desc: Use image node_id 2 for calling a global function with example usage: test_euler_pendulum() without return types