def _minpoly_cos(ex, x): """ Returns the minimal polynomial of ``cos(ex)`` see http://mathworld.wolfram.com/TrigonometryAngles.html """ c, a = ex.args[0].as_coeff_Mul() if a is pi: if c.is_rational: if c.p == 1: if c.q == 7: return 8 * x**3 - 4 * x**2 - 4 * x + 1 if c.q == 9: return 8 * x**3 - 6 * x - 1 elif c.p == 2: q = sympify(c.q) if q.is_prime: s = _minpoly_sin(ex, x) return _mexpand(s.subs({x: sqrt((1 - x) / 2)})) # for a = pi*p/q, cos(q*a) =T_q(cos(a)) = (-1)**p n = int(c.q) a = dup_chebyshevt(n, ZZ) a = [x**(n - i) * a[i] for i in range(n + 1)] r = Add(*a) - (-1)**c.p _, factors = factor_list(r) res = _choose_factor(factors, x, ex) return res raise NotAlgebraic("%s does not seem to be an algebraic element" % ex)
def _minpoly_cos(ex, x): """ Returns the minimal polynomial of ``cos(ex)`` see http://mathworld.wolfram.com/TrigonometryAngles.html """ from sympy import sqrt c, a = ex.args[0].as_coeff_Mul() if a is pi: if c.is_rational: if c.p == 1: if c.q == 7: return 8*x**3 - 4*x**2 - 4*x + 1 if c.q == 9: return 8*x**3 - 6*x + 1 elif c.p == 2: q = sympify(c.q) if q.is_prime: s = _minpoly_sin(ex, x) return _mexpand(s.subs({x:sqrt((1 - x)/2)})) # for a = pi*p/q, cos(q*a) =T_q(cos(a)) = (-1)**p n = int(c.q) a = dup_chebyshevt(n, ZZ) a = [x**(n - i)*a[i] for i in range(n + 1)] r = Add(*a) - (-1)**c.p _, factors = factor_list(r) res = _choose_factor(factors, x, ex) return res raise NotAlgebraic("%s doesn't seem to be an algebraic element" % ex)
def _minpoly_sin(ex, x): """ Returns the minimal polynomial of ``sin(ex)`` see http://mathworld.wolfram.com/TrigonometryAngles.html """ from sympy.functions.combinatorial.factorials import binomial c, a = ex.args[0].as_coeff_Mul() if a is pi: if c.is_rational: n = c.q q = sympify(n) if q.is_prime: # for a = pi*p/q with q odd prime, using chebyshevt # write sin(q*a) = mp(sin(a))*sin(a); # the roots of mp(x) are sin(pi*p/q) for p = 1,..., q - 1 a = dup_chebyshevt(n, ZZ) return Add(*[x**(n - i - 1)*a[i] for i in range(n)]) if c.p == 1: if q == 9: return 64*x**6 - 96*x**4 + 36*x**2 - 3 if n % 2 == 1: # for a = pi*p/q with q odd, use # sin(q*a) = 0 to see that the minimal polynomial must be # a factor of dup_chebyshevt(n, ZZ) a = dup_chebyshevt(n, ZZ) a = [x**(n - i)*a[i] for i in range(n + 1)] r = Add(*a) _, factors = factor_list(r) res = _choose_factor(factors, x, ex) return res expr = ((1 - C.cos(2*c*pi))/2)**S.Half res = _minpoly_compose(expr, x, QQ) return res raise NotAlgebraic("%s doesn't seem to be an algebraic element" % ex)
def _minpoly_sin(ex, x): """ Returns the minimal polynomial of ``sin(ex)`` see http://mathworld.wolfram.com/TrigonometryAngles.html """ from sympy.functions.combinatorial.factorials import binomial c, a = ex.args[0].as_coeff_Mul() if a is pi: if c.is_rational: n = c.q q = sympify(n) if q.is_prime: # for a = pi*p/q with q odd prime, using chebyshevt # write sin(q*a) = mp(sin(a))*sin(a); # the roots of mp(x) are sin(pi*p/q) for p = 1,..., q - 1 a = dup_chebyshevt(n, ZZ) return Add(*[x**(n - i - 1) * a[i] for i in range(n)]) if c.p == 1: if q == 9: return 64 * x**6 - 96 * x**4 + 36 * x**2 - 3 if n % 2 == 1: # for a = pi*p/q with q odd, use # sin(q*a) = 0 to see that the minimal polynomial must be # a factor of dup_chebyshevt(n, ZZ) a = dup_chebyshevt(n, ZZ) a = [x**(n - i) * a[i] for i in range(n + 1)] r = Add(*a) _, factors = factor_list(r) res = _choose_factor(factors, x, ex) return res expr = ((1 - C.cos(2 * c * pi)) / 2)**S.Half res = _minpoly_compose(expr, x, QQ) return res raise NotAlgebraic("%s doesn't seem to be an algebraic element" % ex)