def test_sympyissue_6208():
assert sqrt(33**(9*I/10)) == -33**(9*I/20)
assert root((6*I)**(2*I), 3).as_base_exp()[1] == Rational(1, 3) # != 2*I/3
assert root((6*I)**(I/3), 3).as_base_exp()[1] == I/9
assert sqrt(exp(3*I)) == exp(3*I/2)
assert sqrt(-sqrt(3)*(1 + 2*I)) == sqrt(sqrt(3))*sqrt(-1 - 2*I)
assert sqrt(exp(5*I)) == -exp(5*I/2)
assert root(exp(5*I), 3).exp == Rational(1, 3)
def test_sympyissue_6208():
assert sqrt(33**(9*I/10)) == -33**(9*I/20)
assert root((6*I)**(2*I), 3).as_base_exp()[1] == Rational(1, 3) # != 2*I/3
assert root((6*I)**(I/3), 3).as_base_exp()[1] == I/9
assert sqrt(exp(3*I)) == exp(3*I/2)
assert sqrt(-sqrt(3)*(1 + 2*I)) == sqrt(sqrt(3))*sqrt(-1 - 2*I)
assert sqrt(exp(5*I)) == -exp(5*I/2)
assert root(exp(5*I), 3).exp == Rational(1, 3)
def roots_cyclotomic(f, factor=False):
"""Compute roots of cyclotomic polynomials. """
L, U = _inv_totient_estimate(f.degree())
for n in range(L, U + 1):
g = cyclotomic_poly(n, f.gen, polys=True)
if f == g:
break
else: # pragma: no cover
raise RuntimeError("failed to find index of a cyclotomic polynomial")
roots = []
if not factor:
# get the indices in the right order so the computed
# roots will be sorted
h = n//2
ks = [i for i in range(1, n + 1) if igcd(i, n) == 1]
ks.sort(key=lambda x: (x, -1) if x <= h else (abs(x - n), 1))
d = 2*I*pi/n
for k in reversed(ks):
roots.append(exp(k*d).expand(complex=True))
else:
g = Poly(f, extension=root(-1, n))
for h, _ in ordered(g.factor_list()[1]):
roots.append(-h.TC())
return roots
def test_sympyissue_12578():
s = root(1 - ((x - 1/x)/2)**(-4), 8)
assert s.series(x, n=17) == (1 - 2*x**4 - 8*x**6 - 34*x**8 -
152*x**10 - 714*x**12 - 3472*x**14 -
17318*x**16 + O(x**17))
d10 = s.diff(x, 10)
assert d10.limit(x, 0) == -551577600
def test_sympyissue_12578():
s = root(1 - ((x - 1/x)/2)**(-4), 8)
assert s.series(x, n=17) == (1 - 2*x**4 - 8*x**6 - 34*x**8 -
152*x**10 - 714*x**12 - 3472*x**14 -
17318*x**16 + O(x**17))
d10 = s.diff(x, 10)
assert d10.limit(x, 0) == -551577600
def roots_binomial(f):
"""Returns a list of roots of a binomial polynomial. If the domain is ZZ
then the roots will be sorted with negatives coming before positives.
The ordering will be the same for any numerical coefficients as long as
the assumptions tested are correct, otherwise the ordering will not be
sorted (but will be canonical).
"""
n = f.degree()
a, b = f.nth(n), f.nth(0)
base = -cancel(b/a)
alpha = root(base, n)
if alpha.is_number:
alpha = alpha.expand(complex=True)
# define some parameters that will allow us to order the roots.
# If the domain is ZZ this is guaranteed to return roots sorted
# with reals before non-real roots and non-real sorted according
# to real part and imaginary part, e.g. -1, 1, -1 + I, 2 - I
neg = base.is_negative
even = n % 2 == 0
if neg:
if even and (base + 1).is_positive:
big = True
else:
big = False
# get the indices in the right order so the computed
# roots will be sorted when the domain is ZZ
ks = []
imax = n//2
if even:
ks.append(imax)
imax -= 1
if not neg:
ks.append(0)
for i in range(imax, 0, -1):
if neg:
ks.extend([i, -i])
else:
ks.extend([-i, i])
if neg:
ks.append(0)
if big:
for i in range(0, len(ks), 2):
pair = ks[i: i + 2]
pair = list(reversed(pair))
# compute the roots
roots, d = [], 2*I*pi/n
for k in ks:
zeta = exp(k*d).expand(complex=True)
roots.append((alpha*zeta).expand(power_base=False))
return roots
def taylor_term(n, x, *previous_terms):
if n < 0:
return S.Zero
else:
x = sympify(x)
if len(previous_terms) > 1:
p = previous_terms[-1]
return (3**Rational(1, 3) * x *
Abs(sin(2 * pi *
(n + S.One) / Integer(3))) * factorial(
(n - S.One) / Integer(3)) /
((n + S.One) *
Abs(cos(2 * pi *
(n + S.Half) / Integer(3))) * factorial(
(n - 2) / Integer(3))) * p)
else:
return (S.One / (root(3, 6) * pi) * gamma(
(n + S.One) / Integer(3)) *
Abs(sin(2 * pi * (n + S.One) / Integer(3))) /
factorial(n) * (root(3, 3) * x)**n)
def taylor_term(n, x, *previous_terms):
if n < 0:
return S.Zero
else:
x = sympify(x)
if len(previous_terms) > 1:
p = previous_terms[-1]
return ((3**Rational(1, 3) * x)**(-n) *
(3**Rational(1, 3) * x)**(n + 1) *
sin(pi * (2 * n / 3 + Rational(4, 3))) * factorial(n) *
gamma(n / 3 + Rational(2, 3)) /
(sin(pi * (2 * n / 3 + Rational(2, 3))) *
factorial(n + 1) * gamma(n / 3 + Rational(1, 3))) * p)
else:
return (S.One / (3**Rational(2, 3) * pi) * gamma(
(n + S.One) / Integer(3)) * sin(2 * pi *
(n + S.One) / Integer(3)) /
factorial(n) * (root(3, 3) * x)**n)
def test_real_root():
assert real_root(-8, 3) == -2
assert real_root(-16, 4) == root(-16, 4)
r = root(-7, 4)
assert real_root(r) == r
r1 = root(-1, 3)
r2 = r1**2
r3 = root(-1, 4)
assert real_root(r1 + r2 + r3) == -1 + r2 + r3
assert real_root(root(-2, 3)) == -root(2, 3)
assert real_root(-8., 3) == -2
x = Symbol('x')
n = Symbol('n')
g = real_root(x, n)
assert g.subs(dict(x=-8, n=3)) == -2
assert g.subs(dict(x=8, n=3)) == 2
# give principle root if there is no real root -- if this is not desired
# then maybe a Root class is needed to raise an error instead
assert g.subs(dict(x=I, n=3)) == cbrt(I)
assert g.subs(dict(x=-8, n=2)) == sqrt(-8)
assert g.subs(dict(x=I, n=2)) == sqrt(I)
def roots_cubic(f, trig=False):
"""Returns a list of roots of a cubic polynomial.
References
==========
.. [1] https://en.wikipedia.org/wiki/Cubic_function, General
formula for roots, (accessed November 17, 2014).
"""
if trig:
a, b, c, d = f.all_coeffs()
p = (3*a*c - b**2)/3/a**2
q = (2*b**3 - 9*a*b*c + 27*a**2*d)/(27*a**3)
D = 18*a*b*c*d - 4*b**3*d + b**2*c**2 - 4*a*c**3 - 27*a**2*d**2
if (D > 0) is S.true:
rv = []
for k in range(3):
rv.append(2*sqrt(-p/3)*cos(acos(3*q/2/p*sqrt(-3/p))/3 - k*2*pi/3))
return [i - b/3/a for i in rv]
_, a, b, c = f.monic().all_coeffs()
if c is S.Zero:
x1, x2 = roots([1, a, b], multiple=True)
return [x1, S.Zero, x2]
p = b - a**2/3
q = c - a*b/3 + 2*a**3/27
pon3 = p/3
aon3 = a/3
u1 = None
if p is S.Zero:
if q is S.Zero:
return [-aon3]*3
if q.is_extended_real:
if q.is_positive:
u1 = -root(q, 3)
elif q.is_negative:
u1 = root(-q, 3)
elif q is S.Zero:
y1, y2 = roots([1, 0, p], multiple=True)
return [tmp - aon3 for tmp in [y1, S.Zero, y2]]
elif q.is_extended_real and q.is_negative:
u1 = -root(-q/2 + sqrt(q**2/4 + pon3**3), 3)
coeff = I*sqrt(3)/2
if u1 is None:
u1 = Integer(1)
u2 = -S.Half + coeff
u3 = -S.Half - coeff
a, b, c, d = Integer(1), a, b, c
D0 = b**2 - 3*a*c
D1 = 2*b**3 - 9*a*b*c + 27*a**2*d
C = root((D1 + sqrt(D1**2 - 4*D0**3))/2, 3)
return [-(b + uk*C + D0/C/uk)/3/a for uk in [u1, u2, u3]]
u2 = u1*(-S.Half + coeff)
u3 = u1*(-S.Half - coeff)
if p is S.Zero:
return [u1 - aon3, u2 - aon3, u3 - aon3]
soln = [
-u1 + pon3/u1 - aon3,
-u2 + pon3/u2 - aon3,
-u3 + pon3/u3 - aon3
]
return soln
def test_root():
from diofant.abc import x
n = Symbol('n', integer=True)
k = Symbol('k', integer=True)
assert root(2, 2) == sqrt(2)
assert root(2, 1) == 2
assert root(2, 3) == 2**Rational(1, 3)
assert root(2, 3) == cbrt(2)
assert root(2, -5) == 2**Rational(4, 5) / 2
assert root(-2, 1) == -2
assert root(-2, 2) == sqrt(2) * I
assert root(-2, 1) == -2
assert root(x, 2) == sqrt(x)
assert root(x, 1) == x
assert root(x, 3) == x**Rational(1, 3)
assert root(x, 3) == cbrt(x)
assert root(x, -5) == x**Rational(-1, 5)
assert root(x, n) == x**(1 / n)
assert root(x, -n) == x**(-1 / n)
assert root(x, n, k) == x**(1 / n) * (-1)**(2 * k / n)
def _eval_rewrite_as_hyper(self, z):
pf1 = S.One / (3**Rational(2, 3) * gamma(Rational(2, 3)))
pf2 = z / (root(3, 3) * gamma(Rational(1, 3)))
return pf1 * hyper([], [Rational(2, 3)], z**3 / 9) - pf2 * hyper(
[], [Rational(4, 3)], z**3 / 9)
def _eval_rewrite_as_hyper(self, z):
pf1 = z**2 / (2 * root(3, 6) * gamma(Rational(2, 3)))
pf2 = root(3, 6) / gamma(Rational(1, 3))
return pf1 * hyper([], [Rational(5, 3)], z**3 / 9) + pf2 * hyper(
[], [Rational(1, 3)], z**3 / 9)
def _eval_rewrite_as_hyper(self, z):
pf1 = z**2 / (2 * 3**Rational(2, 3) * gamma(Rational(2, 3)))
pf2 = 1 / (root(3, 3) * gamma(Rational(1, 3)))
return pf1 * hyper([], [Rational(5, 3)], z**3 / 9) - pf2 * hyper(
[], [Rational(1, 3)], z**3 / 9)