def test_diff3():
p = Rational(5)
e = a * b + sin(b**p)
assert e == a * b + sin(b**5)
assert e.diff(a) == b
assert e.diff(b) == a + 5 * b**4 * cos(b**5)
e = tan(c)
assert e == tan(c)
assert e.diff(c) in [
cos(c)**(-2), 1 + sin(c)**2 / cos(c)**2, 1 + tan(c)**2
]
e = c * log(c) - c
assert e == -c + c * log(c)
assert e.diff(c) == log(c)
e = log(sin(c))
assert e == log(sin(c))
assert e.diff(c) in [sin(c)**(-1) * cos(c), cot(c)]
e = Rational(2)**a / log(Rational(2))
assert e == 2**a * log(Rational(2))**(-1)
assert e.diff(a) == 2**a
