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from sympy.core.relational import Eq
from sympy.core.singleton import S
from sympy.abc import x, y, z, s, t
from sympy.sets import FiniteSet, EmptySet
from sympy.geometry import Point
from sympy.vector import ImplicitRegion
from sympy.testing.pytest import raises
def test_ImplicitRegion():
ellipse = ImplicitRegion((x, y), (x**2/4 + y**2/16 - 1))
assert ellipse.equation == x**2/4 + y**2/16 - 1
assert ellipse.variables == (x, y)
assert ellipse.degree == 2
r = ImplicitRegion((x, y, z), Eq(x**4 + y**2 - x*y, 6))
assert r.equation == x**4 + y**2 - x*y - 6
assert r.variables == (x, y, z)
assert r.degree == 4
def test_regular_point():
r1 = ImplicitRegion((x,), x**2 - 16)
assert r1.regular_point() == (-4,)
c1 = ImplicitRegion((x, y), x**2 + y**2 - 4)
assert c1.regular_point() == (0, -2)
c2 = ImplicitRegion((x, y), (x - S(5)/2)**2 + y**2 - (S(1)/4)**2)
assert c2.regular_point() == (S(5)/2, -S(1)/4)
c3 = ImplicitRegion((x, y), (y - 5)**2 - 16*(x - 5))
assert c3.regular_point() == (5, 5)
r2 = ImplicitRegion((x, y), x**2 - 4*x*y - 3*y**2 + 4*x + 8*y - 5)
assert r2.regular_point() == (S(4)/7, S(9)/7)
r3 = ImplicitRegion((x, y), x**2 - 2*x*y + 3*y**2 - 2*x - 5*y + 3/2)
raises(ValueError, lambda: r3.regular_point())
def test_singular_points_and_multiplicty():
r1 = ImplicitRegion((x, y, z), Eq(x + y + z, 0))
assert r1.singular_points() == EmptySet
r2 = ImplicitRegion((x, y, z), x*y*z + y**4 -x**2*z**2)
assert r2.singular_points() == FiniteSet((0, 0, z), (x, 0, 0))
assert r2.multiplicity((0, 0, 0)) == 3
assert r2.multiplicity((0, 0, 6)) == 2
r3 = ImplicitRegion((x, y, z), z**2 - x**2 - y**2)
assert r3.singular_points() == FiniteSet((0, 0, 0))
assert r3.multiplicity((0, 0, 0)) == 2
r4 = ImplicitRegion((x, y), x**2 + y**2 - 2*x)
assert r4.singular_points() == EmptySet
assert r4.multiplicity(Point(1, 3)) == 0
def test_rational_parametrization():
p = ImplicitRegion((x,), x - 2)
assert p.rational_parametrization() == (x - 2,)
line = ImplicitRegion((x, y), Eq(y, 3*x + 2))
assert line.rational_parametrization() == (x, 3*x + 2)
circle1 = ImplicitRegion((x, y), (x-2)**2 + (y+3)**2 - 4)
assert circle1.rational_parametrization(parameters=t) == (4*t/(t**2 + 1) + 2, 4*t**2/(t**2 + 1) - 5)
circle2 = ImplicitRegion((x, y), (x - S.Half)**2 + y**2 - (S(1)/2)**2)
assert circle2.rational_parametrization(parameters=t) == (t/(t**2 + 1) + S(1)/2, t**2/(t**2 + 1) - S(1)/2)
circle3 = ImplicitRegion((x, y), Eq(x**2 + y**2, 2*x))
assert circle3.rational_parametrization(parameters=(t,)) == (2*t/(t**2 + 1) + 1, 2*t**2/(t**2 + 1) - 1)
parabola = ImplicitRegion((x, y), (y - 3)**2 - 4*(x + 6))
assert parabola.rational_parametrization(t) == (-6 + 4/t**2, 3 + 4/t)
rect_hyperbola = ImplicitRegion((x, y), x*y - 1)
assert rect_hyperbola.rational_parametrization(t) == (-1 + (t + 1)/t, t)
cubic_curve = ImplicitRegion((x, y), x**3 + x**2 - y**2)
assert cubic_curve.rational_parametrization(parameters=(t)) == (t**2 - 1, t*(t**2 - 1))
cuspidal = ImplicitRegion((x, y), (x**3 - y**2))
assert cuspidal.rational_parametrization(t) == (t**2, t**3)
I = ImplicitRegion((x, y), x**3 + x**2 - y**2)
assert I.rational_parametrization(t) == (t**2 - 1, t*(t**2 - 1))
sphere = ImplicitRegion((x, y, z), Eq(x**2 + y**2 + z**2, 2*x))
assert sphere.rational_parametrization(parameters=(s, t)) == (2/(s**2 + t**2 + 1), 2*t/(s**2 + t**2 + 1), 2*s/(s**2 + t**2 + 1))
conic = ImplicitRegion((x, y), Eq(x**2 + 4*x*y + 3*y**2 + x - y + 10, 0))
assert conic.rational_parametrization(t) == (
S(17)/2 + 4/(3*t**2 + 4*t + 1), 4*t/(3*t**2 + 4*t + 1) - S(11)/2)
r1 = ImplicitRegion((x, y), y**2 - x**3 + x)
raises(NotImplementedError, lambda: r1.rational_parametrization())
r2 = ImplicitRegion((x, y), y**2 - x**3 - x**2 + 1)
raises(NotImplementedError, lambda: r2.rational_parametrization())
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