def test_ADmath_arccosr():
f = ADmath.arccos(.3)
assert f == np.arccos(.3)
def test_ADmath_arccos():
f = ADmath.arccos(ADnum(.3, der=1))
assert f.val == np.arccos(.3)
assert f.der == -1 / (np.sqrt(1 - .3**2))
assert len(f.graph) == 1