def test_issue_6364():
    a = Symbol('a')
    e = z/(1 - sqrt(1 + z)*sin(a)**2 - sqrt(1 - z)*cos(a)**2)
    assert limit(e, z, 0).simplify() == 2/cos(2*a)
dataset/ETHPy150Open sympy/sympy/sympy/series/tests/test_limits.py/test_issue_6364/original