def test_atan():
    a = atan(interval(0, 1))
    assert a.start == np.arctan(0)
    assert a.end == np.arctan(1)
    a = atan(1)
    assert a.start == np.arctan(1)
    assert a.end == np.arctan(1)
def test_atan():
    a = atan(interval(0, 1))
    assert a.start == np.arctan(0)
    assert a.end == np.arctan(1)
    a = atan(1)
    assert a.start == np.arctan(1)
    assert a.end == np.arctan(1)