Beispiel #1
0
def test_hyper_as_trig():
    from sympy.simplify.fu import _osborne, _osbornei

    eq = sinh(x)**2 + cosh(x)**2
    t, f = hyper_as_trig(eq)
    assert f(fu(t)) == cosh(2 * x)
    e, f = hyper_as_trig(tanh(x + y))
    assert f(TR12(e)) == (tanh(x) + tanh(y)) / (tanh(x) * tanh(y) + 1)

    d = Dummy()
    assert _osborne(sinh(x), d) == I * sin(x * d)
    assert _osborne(tanh(x), d) == I * tan(x * d)
    assert _osborne(coth(x), d) == cot(x * d) / I
    assert _osborne(cosh(x), d) == cos(x * d)
    assert _osborne(sech(x), d) == sec(x * d)
    assert _osborne(csch(x), d) == csc(x * d) / I
    for func in (sinh, cosh, tanh, coth, sech, csch):
        h = func(pi)
        assert _osbornei(_osborne(h, d), d) == h
    # /!\ the _osborne functions are not meant to work
    # in the o(i(trig, d), d) direction so we just check
    # that they work as they are supposed to work
    assert _osbornei(cos(x * y + z), y) == cosh(x + z * I)
    assert _osbornei(sin(x * y + z), y) == sinh(x + z * I) / I
    assert _osbornei(tan(x * y + z), y) == tanh(x + z * I) / I
    assert _osbornei(cot(x * y + z), y) == coth(x + z * I) * I
    assert _osbornei(sec(x * y + z), y) == sech(x + z * I)
    assert _osbornei(csc(x * y + z), y) == csch(x + z * I) * I
Beispiel #2
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def test_find_substitutions():
    assert find_substitutions((cot(x)**2 + 1)**2*csc(x)**2*cot(x)**2, x, u) == \
        [(cot(x), 1, -u**6 - 2*u**4 - u**2)]
    assert find_substitutions(
        (sec(x)**2 + tan(x) * sec(x)) / (sec(x) + tan(x)), x,
        u) == [(sec(x) + tan(x), 1, 1 / u)]
    assert (-x**2, Rational(-1, 2),
            exp(u)) in find_substitutions(x * exp(-x**2), x, u)
Beispiel #3
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def test_periodicity_check():
    x = Symbol('x')
    y = Symbol('y')

    assert periodicity(tan(x), x, check=True) == pi
    assert periodicity(sin(x) + cos(x), x, check=True) == 2*pi
    assert periodicity(sec(x), x) == 2*pi
    assert periodicity(sin(x*y), x) == 2*pi/abs(y)
    assert periodicity(Abs(sec(sec(x))), x) == pi
Beispiel #4
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def test_sech():
    x, y = symbols('x, y')

    k = Symbol('k', integer=True)
    n = Symbol('n', positive=True)

    assert sech(nan) is nan
    assert sech(zoo) is nan

    assert sech(oo) == 0
    assert sech(-oo) == 0

    assert sech(0) == 1

    assert sech(-1) == sech(1)
    assert sech(-x) == sech(x)

    assert sech(pi * I) == sec(pi)

    assert sech(-pi * I) == sec(pi)
    assert sech(-2**1024 * E) == sech(2**1024 * E)

    assert sech(pi * I / 2) is zoo
    assert sech(-pi * I / 2) is zoo
    assert sech((-3 * 10**73 + 1) * pi * I / 2) is zoo
    assert sech((7 * 10**103 + 1) * pi * I / 2) is zoo

    assert sech(pi * I) == -1
    assert sech(-pi * I) == -1
    assert sech(5 * pi * I) == -1
    assert sech(8 * pi * I) == 1

    assert sech(pi * I / 3) == 2
    assert sech(pi * I * Rational(-2, 3)) == -2

    assert sech(pi * I / 4) == sqrt(2)
    assert sech(-pi * I / 4) == sqrt(2)
    assert sech(pi * I * Rational(5, 4)) == -sqrt(2)
    assert sech(pi * I * Rational(-5, 4)) == -sqrt(2)

    assert sech(pi * I / 6) == 2 / sqrt(3)
    assert sech(-pi * I / 6) == 2 / sqrt(3)
    assert sech(pi * I * Rational(7, 6)) == -2 / sqrt(3)
    assert sech(pi * I * Rational(-5, 6)) == -2 / sqrt(3)

    assert sech(pi * I / 105) == 1 / cos(pi / 105)
    assert sech(-pi * I / 105) == 1 / cos(pi / 105)

    assert sech(x * I) == 1 / cos(x)

    assert sech(k * pi * I) == 1 / cos(k * pi)
    assert sech(17 * k * pi * I) == 1 / cos(17 * k * pi)

    assert sech(n).is_real is True

    assert expand_trig(sech(x +
                            y)) == 1 / (cosh(x) * cosh(y) + sinh(x) * sinh(y))
Beispiel #5
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def test_manualintegrate_trigonometry():
    assert manualintegrate(sin(x), x) == -cos(x)
    assert manualintegrate(tan(x), x) == -log(cos(x))

    assert manualintegrate(sec(x), x) == log(sec(x) + tan(x))
    assert manualintegrate(csc(x), x) == -log(csc(x) + cot(x))

    assert manualintegrate(sin(x) * cos(x),
                           x) in [sin(x)**2 / 2, -cos(x)**2 / 2]
    assert manualintegrate(-sec(x) * tan(x), x) == -sec(x)
    assert manualintegrate(csc(x) * cot(x), x) == -csc(x)
    assert manualintegrate(sec(x)**2, x) == tan(x)
    assert manualintegrate(csc(x)**2, x) == -cot(x)

    assert manualintegrate(x * sec(x**2), x) == log(tan(x**2) + sec(x**2)) / 2
    assert manualintegrate(cos(x) * csc(sin(x)),
                           x) == -log(cot(sin(x)) + csc(sin(x)))
    assert manualintegrate(cos(3 * x) * sec(x), x) == -x + sin(2 * x)
    assert manualintegrate(sin(3*x)*sec(x), x) == \
        -3*log(cos(x)) + 2*log(cos(x)**2) - 2*cos(x)**2

    assert_is_integral_of(sinh(2 * x), cosh(2 * x) / 2)
    assert_is_integral_of(x * cosh(x**2), sinh(x**2) / 2)
    assert_is_integral_of(tanh(x), log(cosh(x)))
    assert_is_integral_of(coth(x), log(sinh(x)))
    f, F = sech(x), 2 * atan(tanh(x / 2))
    assert manualintegrate(f, x) == F
    assert (F.diff(x) -
            f).rewrite(exp).simplify() == 0  # todo: equals returns None
    f, F = csch(x), log(tanh(x / 2))
    assert manualintegrate(f, x) == F
    assert (F.diff(x) - f).rewrite(exp).simplify() == 0
Beispiel #6
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def test_manualintegrate_trigpowers():
    assert manualintegrate(sin(x)**2 * cos(x), x) == sin(x)**3 / 3
    assert manualintegrate(sin(x)**2 * cos(x) **2, x) == \
        x / 8 - sin(4*x) / 32
    assert manualintegrate(sin(x) * cos(x)**3, x) == -cos(x)**4 / 4
    assert manualintegrate(sin(x)**3 * cos(x)**2, x) == \
        cos(x)**5 / 5 - cos(x)**3 / 3

    assert manualintegrate(tan(x)**3 * sec(x), x) == sec(x)**3 / 3 - sec(x)
    assert manualintegrate(tan(x) * sec(x)**2, x) == sec(x)**2 / 2

    assert manualintegrate(cot(x)**5 * csc(x), x) == \
        -csc(x)**5/5 + 2*csc(x)**3/3 - csc(x)
    assert manualintegrate(cot(x)**2 * csc(x)**6, x) == \
        -cot(x)**7/7 - 2*cot(x)**5/5 - cot(x)**3/3
Beispiel #7
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def test_stationary_points():
    x, y = symbols('x y')

    assert stationary_points(sin(x), x, Interval(-pi/2, pi/2)
        ) == {-pi/2, pi/2}
    assert  stationary_points(sin(x), x, Interval.Ropen(0, pi/4)
        ) is S.EmptySet
    assert stationary_points(tan(x), x,
        ) is S.EmptySet
    assert stationary_points(sin(x)*cos(x), x, Interval(0, pi)
        ) == {pi/4, pi*Rational(3, 4)}
    assert stationary_points(sec(x), x, Interval(0, pi)
        ) == {0, pi}
    assert stationary_points((x+3)*(x-2), x
        ) == FiniteSet(Rational(-1, 2))
    assert stationary_points((x + 3)/(x - 2), x, Interval(-5, 5)
        ) is S.EmptySet
    assert stationary_points((x**2+3)/(x-2), x
        ) == {2 - sqrt(7), 2 + sqrt(7)}
    assert stationary_points((x**2+3)/(x-2), x, Interval(0, 5)
        ) == {2 + sqrt(7)}
    assert stationary_points(x**4 + x**3 - 5*x**2, x, S.Reals
        ) == FiniteSet(-2, 0, Rational(5, 4))
    assert stationary_points(exp(x), x
        ) is S.EmptySet
    assert stationary_points(log(x) - x, x, S.Reals
        ) == {1}
    assert stationary_points(cos(x), x, Union(Interval(0, 5), Interval(-6, -3))
        ) == {0, -pi, pi}
    assert stationary_points(y, x, S.Reals
        ) == S.Reals
    assert stationary_points(y, x, S.EmptySet) == S.EmptySet
Beispiel #8
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def test_construction():
    e1 = Ellipse(hradius=2, vradius=1, eccentricity=None)
    assert e1.eccentricity == sqrt(3)/2

    e2 = Ellipse(hradius=2, vradius=None, eccentricity=sqrt(3)/2)
    assert e2.vradius == 1

    e3 = Ellipse(hradius=None, vradius=1, eccentricity=sqrt(3)/2)
    assert e3.hradius == 2

    # filter(None, iterator) filters out anything falsey, including 0
    # eccentricity would be filtered out in this case and the constructor would throw an error
    e4 = Ellipse(Point(0, 0), hradius=1, eccentricity=0)
    assert e4.vradius == 1

    #tests for eccentricity > 1
    raises(GeometryError, lambda: Ellipse(Point(3, 1), hradius=3, eccentricity = S(3)/2))
    raises(GeometryError, lambda: Ellipse(Point(3, 1), hradius=3, eccentricity=sec(5)))
    raises(GeometryError, lambda: Ellipse(Point(3, 1), hradius=3, eccentricity=S.Pi-S(2)))

    #tests for eccentricity = 1
    #if vradius is not defined
    assert Ellipse(None, 1, None, 1).length == 2
    #if hradius is not defined
    raises(GeometryError, lambda: Ellipse(None, None, 1, eccentricity = 1))

    #tests for eccentricity < 0
    raises(GeometryError, lambda: Ellipse(Point(3, 1), hradius=3, eccentricity = -3))
    raises(GeometryError, lambda: Ellipse(Point(3, 1), hradius=3, eccentricity = -0.5))
    def f(rv):
        if not (isinstance(rv, Pow) and
                (rv.base.is_positive
                 or rv.exp.is_integer and rv.exp.is_negative)):
            return rv

        if isinstance(rv.base, tan):
            return cot(rv.base.args[0])**-rv.exp
        elif isinstance(rv.base, sin):
            return csc(rv.base.args[0])**-rv.exp
        elif isinstance(rv.base, cos):
            return sec(rv.base.args[0])**-rv.exp
        return rv
Beispiel #10
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def test_manualintegrate_trigonometry():
    assert manualintegrate(sin(x), x) == -cos(x)
    assert manualintegrate(tan(x), x) == -log(cos(x))

    assert manualintegrate(sec(x), x) == log(sec(x) + tan(x))
    assert manualintegrate(csc(x), x) == -log(csc(x) + cot(x))

    assert manualintegrate(sin(x) * cos(x),
                           x) in [sin(x)**2 / 2, -cos(x)**2 / 2]
    assert manualintegrate(-sec(x) * tan(x), x) == -sec(x)
    assert manualintegrate(csc(x) * cot(x), x) == -csc(x)
    assert manualintegrate(sec(x)**2, x) == tan(x)
    assert manualintegrate(csc(x)**2, x) == -cot(x)

    assert manualintegrate(x * sec(x**2), x) == log(tan(x**2) + sec(x**2)) / 2
    assert manualintegrate(cos(x) * csc(sin(x)),
                           x) == -log(cot(sin(x)) + csc(sin(x)))
    assert manualintegrate(cos(3 * x) * sec(x), x) == -x + sin(2 * x)
    assert manualintegrate(sin(3*x)*sec(x), x) == \
        -3*log(cos(x)) + 2*log(cos(x)**2) - 2*cos(x)**2
Beispiel #11
0
    def eval(cls, n, a, x):
        # For negative n the polynomials vanish
        # See http://functions.wolfram.com/Polynomials/GegenbauerC3/03/01/03/0012/
        if n.is_negative:
            return S.Zero

        # Some special values for fixed a
        if a == S.Half:
            return legendre(n, x)
        elif a == S.One:
            return chebyshevu(n, x)
        elif a == S.NegativeOne:
            return S.Zero

        if not n.is_Number:
            # Handle this before the general sign extraction rule
            if x == S.NegativeOne:
                if (re(a) > S.Half) == True:
                    return S.ComplexInfinity
                else:
                    return (
                        cos(S.Pi * (a + n))
                        * sec(S.Pi * a)
                        * gamma(2 * a + n)
                        / (gamma(2 * a) * gamma(n + 1))
                    )

            # Symbolic result C^a_n(x)
            # C^a_n(-x)  --->  (-1)**n * C^a_n(x)
            if x.could_extract_minus_sign():
                return S.NegativeOne ** n * gegenbauer(n, a, -x)
            # We can evaluate for some special values of x
            if x.is_zero:
                return (
                    2 ** n
                    * sqrt(S.Pi)
                    * gamma(a + S.Half * n)
                    / (gamma((1 - n) / 2) * gamma(n + 1) * gamma(a))
                )
            if x == S.One:
                return gamma(2 * a + n) / (gamma(2 * a) * gamma(n + 1))
            elif x is S.Infinity:
                if n.is_positive:
                    return RisingFactorial(a, n) * S.Infinity
        else:
            # n is a given fixed integer, evaluate into polynomial
            return gegenbauer_poly(n, a, x)
 def f(rv):
     if not isinstance(rv, HyperbolicFunction):
         return rv
     a = rv.args[0]
     a = a * d if not a.is_Add else Add._from_args([i * d for i in a.args])
     if isinstance(rv, sinh):
         return I * sin(a)
     elif isinstance(rv, cosh):
         return cos(a)
     elif isinstance(rv, tanh):
         return I * tan(a)
     elif isinstance(rv, coth):
         return cot(a) / I
     elif isinstance(rv, sech):
         return sec(a)
     elif isinstance(rv, csch):
         return csc(a) / I
     else:
         raise NotImplementedError('unhandled %s' % rv.func)
Beispiel #13
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def test_TR1():
    assert TR1(2 * csc(x) + sec(x)) == 1 / cos(x) + 2 / sin(x)
Beispiel #14
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def test_issue_14411():
    assert limit(3*sec(4*pi*x - x/3), x, 3*pi/(24*pi - 2)) is -oo
Beispiel #15
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def test_basic1():
    assert limit(x, x, oo) is oo
    assert limit(x, x, -oo) is -oo
    assert limit(-x, x, oo) is -oo
    assert limit(x**2, x, -oo) is oo
    assert limit(-x**2, x, oo) is -oo
    assert limit(x*log(x), x, 0, dir="+") == 0
    assert limit(1/x, x, oo) == 0
    assert limit(exp(x), x, oo) is oo
    assert limit(-exp(x), x, oo) is -oo
    assert limit(exp(x)/x, x, oo) is oo
    assert limit(1/x - exp(-x), x, oo) == 0
    assert limit(x + 1/x, x, oo) is oo
    assert limit(x - x**2, x, oo) is -oo
    assert limit((1 + x)**(1 + sqrt(2)), x, 0) == 1
    assert limit((1 + x)**oo, x, 0) == Limit((x + 1)**oo, x, 0)
    assert limit((1 + x)**oo, x, 0, dir='-') == Limit((x + 1)**oo, x, 0, dir='-')
    assert limit((1 + x + y)**oo, x, 0, dir='-') == Limit((1 + x + y)**oo, x, 0, dir='-')
    assert limit(y/x/log(x), x, 0) == -oo*sign(y)
    assert limit(cos(x + y)/x, x, 0) == sign(cos(y))*oo
    assert limit(gamma(1/x + 3), x, oo) == 2
    assert limit(S.NaN, x, -oo) is S.NaN
    assert limit(Order(2)*x, x, S.NaN) is S.NaN
    assert limit(1/(x - 1), x, 1, dir="+") is oo
    assert limit(1/(x - 1), x, 1, dir="-") is -oo
    assert limit(1/(5 - x)**3, x, 5, dir="+") is -oo
    assert limit(1/(5 - x)**3, x, 5, dir="-") is oo
    assert limit(1/sin(x), x, pi, dir="+") is -oo
    assert limit(1/sin(x), x, pi, dir="-") is oo
    assert limit(1/cos(x), x, pi/2, dir="+") is -oo
    assert limit(1/cos(x), x, pi/2, dir="-") is oo
    assert limit(1/tan(x**3), x, (2*pi)**Rational(1, 3), dir="+") is oo
    assert limit(1/tan(x**3), x, (2*pi)**Rational(1, 3), dir="-") is -oo
    assert limit(1/cot(x)**3, x, (pi*Rational(3, 2)), dir="+") is -oo
    assert limit(1/cot(x)**3, x, (pi*Rational(3, 2)), dir="-") is oo
    assert limit(tan(x), x, oo) == AccumBounds(S.NegativeInfinity, S.Infinity)
    assert limit(cot(x), x, oo) == AccumBounds(S.NegativeInfinity, S.Infinity)
    assert limit(sec(x), x, oo) == AccumBounds(S.NegativeInfinity, S.Infinity)
    assert limit(csc(x), x, oo) == AccumBounds(S.NegativeInfinity, S.Infinity)

    # test bi-directional limits
    assert limit(sin(x)/x, x, 0, dir="+-") == 1
    assert limit(x**2, x, 0, dir="+-") == 0
    assert limit(1/x**2, x, 0, dir="+-") is oo

    # test failing bi-directional limits
    assert limit(1/x, x, 0, dir="+-") is zoo
    # approaching 0
    # from dir="+"
    assert limit(1 + 1/x, x, 0) is oo
    # from dir='-'
    # Add
    assert limit(1 + 1/x, x, 0, dir='-') is -oo
    # Pow
    assert limit(x**(-2), x, 0, dir='-') is oo
    assert limit(x**(-3), x, 0, dir='-') is -oo
    assert limit(1/sqrt(x), x, 0, dir='-') == (-oo)*I
    assert limit(x**2, x, 0, dir='-') == 0
    assert limit(sqrt(x), x, 0, dir='-') == 0
    assert limit(x**-pi, x, 0, dir='-') == oo/(-1)**pi
    assert limit((1 + cos(x))**oo, x, 0) == Limit((cos(x) + 1)**oo, x, 0)

    # test pull request 22491
    assert limit(1/asin(x), x, 0, dir = '+') == oo
    assert limit(1/asin(x), x, 0, dir = '-') == -oo
    assert limit(1/sinh(x), x, 0, dir = '+') == oo
    assert limit(1/sinh(x), x, 0, dir = '-') == -oo
    assert limit(log(1/x) + 1/sin(x), x, 0, dir = '+') == oo
    assert limit(log(1/x) + 1/x, x, 0, dir = '+') == oo
Beispiel #16
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def test_periodicity():
    x = Symbol('x')
    y = Symbol('y')
    z = Symbol('z', real=True)

    assert periodicity(sin(2*x), x) == pi
    assert periodicity((-2)*tan(4*x), x) == pi/4
    assert periodicity(sin(x)**2, x) == 2*pi
    assert periodicity(3**tan(3*x), x) == pi/3
    assert periodicity(tan(x)*cos(x), x) == 2*pi
    assert periodicity(sin(x)**(tan(x)), x) == 2*pi
    assert periodicity(tan(x)*sec(x), x) == 2*pi
    assert periodicity(sin(2*x)*cos(2*x) - y, x) == pi/2
    assert periodicity(tan(x) + cot(x), x) == pi
    assert periodicity(sin(x) - cos(2*x), x) == 2*pi
    assert periodicity(sin(x) - 1, x) == 2*pi
    assert periodicity(sin(4*x) + sin(x)*cos(x), x) == pi
    assert periodicity(exp(sin(x)), x) == 2*pi
    assert periodicity(log(cot(2*x)) - sin(cos(2*x)), x) == pi
    assert periodicity(sin(2*x)*exp(tan(x) - csc(2*x)), x) == pi
    assert periodicity(cos(sec(x) - csc(2*x)), x) == 2*pi
    assert periodicity(tan(sin(2*x)), x) == pi
    assert periodicity(2*tan(x)**2, x) == pi
    assert periodicity(sin(x%4), x) == 4
    assert periodicity(sin(x)%4, x) == 2*pi
    assert periodicity(tan((3*x-2)%4), x) == Rational(4, 3)
    assert periodicity((sqrt(2)*(x+1)+x) % 3, x) == 3 / (sqrt(2)+1)
    assert periodicity((x**2+1) % x, x) is None
    assert periodicity(sin(re(x)), x) == 2*pi
    assert periodicity(sin(x)**2 + cos(x)**2, x) is S.Zero
    assert periodicity(tan(x), y) is S.Zero
    assert periodicity(sin(x) + I*cos(x), x) == 2*pi
    assert periodicity(x - sin(2*y), y) == pi

    assert periodicity(exp(x), x) is None
    assert periodicity(exp(I*x), x) == 2*pi
    assert periodicity(exp(I*z), z) == 2*pi
    assert periodicity(exp(z), z) is None
    assert periodicity(exp(log(sin(z) + I*cos(2*z)), evaluate=False), z) == 2*pi
    assert periodicity(exp(log(sin(2*z) + I*cos(z)), evaluate=False), z) == 2*pi
    assert periodicity(exp(sin(z)), z) == 2*pi
    assert periodicity(exp(2*I*z), z) == pi
    assert periodicity(exp(z + I*sin(z)), z) is None
    assert periodicity(exp(cos(z/2) + sin(z)), z) == 4*pi
    assert periodicity(log(x), x) is None
    assert periodicity(exp(x)**sin(x), x) is None
    assert periodicity(sin(x)**y, y) is None

    assert periodicity(Abs(sin(Abs(sin(x)))), x) == pi
    assert all(periodicity(Abs(f(x)), x) == pi for f in (
        cos, sin, sec, csc, tan, cot))
    assert periodicity(Abs(sin(tan(x))), x) == pi
    assert periodicity(Abs(sin(sin(x) + tan(x))), x) == 2*pi
    assert periodicity(sin(x) > S.Half, x) == 2*pi

    assert periodicity(x > 2, x) is None
    assert periodicity(x**3 - x**2 + 1, x) is None
    assert periodicity(Abs(x), x) is None
    assert periodicity(Abs(x**2 - 1), x) is None

    assert periodicity((x**2 + 4)%2, x) is None
    assert periodicity((E**x)%3, x) is None

    assert periodicity(sin(expint(1, x))/expint(1, x), x) is None
    # returning `None` for any Piecewise
    p = Piecewise((0, x < -1), (x**2, x <= 1), (log(x), True))
    assert periodicity(p, x) is None

    m = MatrixSymbol('m', 3, 3)
    raises(NotImplementedError, lambda: periodicity(sin(m), m))
    raises(NotImplementedError, lambda: periodicity(sin(m[0, 0]), m))
    raises(NotImplementedError, lambda: periodicity(sin(m), m[0, 0]))
    raises(NotImplementedError, lambda: periodicity(sin(m[0, 0]), m[0, 0]))
Beispiel #17
0
def test_issue_16161():
    i = integrate(x * sec(x)**2, x)
    assert not i.has(Integral)
Beispiel #18
0
 (r"\lfloor x \rfloor", floor(x)),
 (r"\lceil x \rceil", ceiling(x)),
 (r"\langle x |", Bra('x')),
 (r"| x \rangle", Ket('x')),
 (r"\sin \theta", sin(theta)),
 (r"\sin(\theta)", sin(theta)),
 (r"\sin^{-1} a", asin(a)),
 (r"\sin a \cos b", _Mul(sin(a), cos(b))),
 (r"\sin \cos \theta", sin(cos(theta))),
 (r"\sin(\cos \theta)", sin(cos(theta))),
 (r"\frac{a}{b}", a / b),
 (r"\dfrac{a}{b}", a / b),
 (r"\tfrac{a}{b}", a / b),
 (r"\frac{a + b}{c}", _Mul(a + b, _Pow(c, -1))),
 (r"\frac{7}{3}", _Mul(7, _Pow(3, -1))),
 (r"(\csc x)(\sec y)", csc(x) * sec(y)),
 (r"\lim_{x \to 3} a", Limit(a, x, 3)),
 (r"\lim_{x \rightarrow 3} a", Limit(a, x, 3)),
 (r"\lim_{x \Rightarrow 3} a", Limit(a, x, 3)),
 (r"\lim_{x \longrightarrow 3} a", Limit(a, x, 3)),
 (r"\lim_{x \Longrightarrow 3} a", Limit(a, x, 3)),
 (r"\lim_{x \to 3^{+}} a", Limit(a, x, 3, dir='+')),
 (r"\lim_{x \to 3^{-}} a", Limit(a, x, 3, dir='-')),
 (r"\infty", oo),
 (r"\lim_{x \to \infty} \frac{1}{x}", Limit(_Pow(x, -1), x, oo)),
 (r"\frac{d}{dx} x", Derivative(x, x)),
 (r"\frac{d}{dt} x", Derivative(x, t)),
 (r"f(x)", f(x)),
 (r"f(x, y)", f(x, y)),
 (r"f(x, y, z)", f(x, y, z)),
 (r"\frac{d f(x)}{dx}", Derivative(f(x), x)),