Ellipses¶
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class sympy.geometry.ellipse.Ellipse(center=None, hradius=None, vradius=None, eccentricity=None, **kwargs)[source]¶
- An elliptical GeometryEntity. - Parameters
- center : Point, optional - Default value is Point(0, 0) - hradius : number or SymPy expression, optional - vradius : number or SymPy expression, optional - eccentricity : number or SymPy expression, optional - Two of \(hradius\), \(vradius\) and \(eccentricity\) must be supplied to create an Ellipse. The third is derived from the two supplied. 
- Raises
- GeometryError - When \(hradius\), \(vradius\) and \(eccentricity\) are incorrectly supplied as parameters. - TypeError - When \(center\) is not a Point. 
 - Notes - Constructed from a center and two radii, the first being the horizontal radius (along the x-axis) and the second being the vertical radius (along the y-axis). - When symbolic value for hradius and vradius are used, any calculation that refers to the foci or the major or minor axis will assume that the ellipse has its major radius on the x-axis. If this is not true then a manual rotation is necessary. - Examples - >>> from sympy import Ellipse, Point, Rational >>> e1 = Ellipse(Point(0, 0), 5, 1) >>> e1.hradius, e1.vradius (5, 1) >>> e2 = Ellipse(Point(3, 1), hradius=3, eccentricity=Rational(4, 5)) >>> e2 Ellipse(Point2D(3, 1), 3, 9/5) - See also - Attributes - center - hradius - vradius - area - circumference - eccentricity - periapsis - apoapsis - focus_distance - foci - 
property apoapsis¶
- The apoapsis of the ellipse. - The greatest distance between the focus and the contour. - Returns
- apoapsis : number 
 - Examples - >>> from sympy import Point, Ellipse >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.apoapsis 2*sqrt(2) + 3 - See also - periapsis
- Returns shortest distance between foci and contour 
 
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arbitrary_point(parameter='t')[source]¶
- A parameterized point on the ellipse. - Parameters
- parameter : str, optional - Default value is ‘t’. 
- Returns
- arbitrary_point : Point 
- Raises
- ValueError - When \(parameter\) already appears in the functions. 
 - Examples - >>> from sympy import Point, Ellipse >>> e1 = Ellipse(Point(0, 0), 3, 2) >>> e1.arbitrary_point() Point2D(3*cos(t), 2*sin(t)) - See also 
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property area¶
- The area of the ellipse. - Returns
- area : number 
 - Examples - >>> from sympy import Point, Ellipse >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.area 3*pi 
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auxiliary_circle()[source]¶
- Returns a Circle whose diameter is the major axis of the ellipse. - Examples - >>> from sympy import Circle, Ellipse, Point, symbols >>> c = Point(1, 2) >>> Ellipse(c, 8, 7).auxiliary_circle() Circle(Point2D(1, 2), 8) >>> a, b = symbols('a b') >>> Ellipse(c, a, b).auxiliary_circle() Circle(Point2D(1, 2), Max(a, b)) 
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property bounds¶
- Return a tuple (xmin, ymin, xmax, ymax) representing the bounding rectangle for the geometric figure. 
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property center¶
- The center of the ellipse. - Returns
- center : number 
 - Examples - >>> from sympy import Point, Ellipse >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.center Point2D(0, 0) - See also 
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property circumference¶
- The circumference of the ellipse. - Examples - >>> from sympy import Point, Ellipse >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.circumference 12*elliptic_e(8/9) 
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director_circle()[source]¶
- Returns a Circle consisting of all points where two perpendicular tangent lines to the ellipse cross each other. - Returns
- Circle - A director circle returned as a geometric object. 
 - Examples - >>> from sympy import Circle, Ellipse, Point, symbols >>> c = Point(3,8) >>> Ellipse(c, 7, 9).director_circle() Circle(Point2D(3, 8), sqrt(130)) >>> a, b = symbols('a b') >>> Ellipse(c, a, b).director_circle() Circle(Point2D(3, 8), sqrt(a**2 + b**2)) - References 
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property eccentricity¶
- The eccentricity of the ellipse. - Returns
- eccentricity : number 
 - Examples - >>> from sympy import Point, Ellipse, sqrt >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, sqrt(2)) >>> e1.eccentricity sqrt(7)/3 
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encloses_point(p)[source]¶
- Return True if p is enclosed by (is inside of) self. - Parameters
- p : Point 
- Returns
- encloses_point : True, False or None 
 - Notes - Being on the border of self is considered False. - Examples - >>> from sympy import Ellipse, S >>> from sympy.abc import t >>> e = Ellipse((0, 0), 3, 2) >>> e.encloses_point((0, 0)) True >>> e.encloses_point(e.arbitrary_point(t).subs(t, S.Half)) False >>> e.encloses_point((4, 0)) False - See also 
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equation(x='x', y='y', _slope=None)[source]¶
- Returns the equation of an ellipse aligned with the x and y axes; when slope is given, the equation returned corresponds to an ellipse with a major axis having that slope. - Parameters
- x : str, optional - Label for the x-axis. Default value is ‘x’. - y : str, optional - Label for the y-axis. Default value is ‘y’. - _slope : Expr, optional - The slope of the major axis. Ignored when ‘None’. 
- Returns
- equation : sympy expression 
 - Examples - >>> from sympy import Point, Ellipse, pi >>> from sympy.abc import x, y >>> e1 = Ellipse(Point(1, 0), 3, 2) >>> eq1 = e1.equation(x, y); eq1 y**2/4 + (x/3 - 1/3)**2 - 1 >>> eq2 = e1.equation(x, y, _slope=1); eq2 (-x + y + 1)**2/8 + (x + y - 1)**2/18 - 1 - A point on e1 satisfies eq1. Let’s use one on the x-axis: - >>> p1 = e1.center + Point(e1.major, 0) >>> assert eq1.subs(x, p1.x).subs(y, p1.y) == 0 - When rotated the same as the rotated ellipse, about the center point of the ellipse, it will satisfy the rotated ellipse’s equation, too: - >>> r1 = p1.rotate(pi/4, e1.center) >>> assert eq2.subs(x, r1.x).subs(y, r1.y) == 0 - See also - arbitrary_point
- Returns parameterized point on ellipse 
 - References 
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evolute(x='x', y='y')[source]¶
- The equation of evolute of the ellipse. - Parameters
- x : str, optional - Label for the x-axis. Default value is ‘x’. - y : str, optional - Label for the y-axis. Default value is ‘y’. 
- Returns
- equation : sympy expression 
 - Examples - >>> from sympy import Point, Ellipse >>> e1 = Ellipse(Point(1, 0), 3, 2) >>> e1.evolute() 2**(2/3)*y**(2/3) + (3*x - 3)**(2/3) - 5**(2/3) 
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property foci¶
- The foci of the ellipse. - Raises
- ValueError - When the major and minor axis cannot be determined. 
 - Notes - The foci can only be calculated if the major/minor axes are known. - Examples - >>> from sympy import Point, Ellipse >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.foci (Point2D(-2*sqrt(2), 0), Point2D(2*sqrt(2), 0)) 
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property focus_distance¶
- The focal distance of the ellipse. - The distance between the center and one focus. - Returns
- focus_distance : number 
 - Examples - >>> from sympy import Point, Ellipse >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.focus_distance 2*sqrt(2) - See also 
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property hradius¶
- The horizontal radius of the ellipse. - Returns
- hradius : number 
 - Examples - >>> from sympy import Point, Ellipse >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.hradius 3 
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intersection(o)[source]¶
- The intersection of this ellipse and another geometrical entity \(o\). - Parameters
- o : GeometryEntity 
- Returns
- intersection : list of GeometryEntity objects 
 - Notes - Currently supports intersections with Point, Line, Segment, Ray, Circle and Ellipse types. - Examples - >>> from sympy import Ellipse, Point, Line, sqrt >>> e = Ellipse(Point(0, 0), 5, 7) >>> e.intersection(Point(0, 0)) [] >>> e.intersection(Point(5, 0)) [Point2D(5, 0)] >>> e.intersection(Line(Point(0,0), Point(0, 1))) [Point2D(0, -7), Point2D(0, 7)] >>> e.intersection(Line(Point(5,0), Point(5, 1))) [Point2D(5, 0)] >>> e.intersection(Line(Point(6,0), Point(6, 1))) [] >>> e = Ellipse(Point(-1, 0), 4, 3) >>> e.intersection(Ellipse(Point(1, 0), 4, 3)) [Point2D(0, -3*sqrt(15)/4), Point2D(0, 3*sqrt(15)/4)] >>> e.intersection(Ellipse(Point(5, 0), 4, 3)) [Point2D(2, -3*sqrt(7)/4), Point2D(2, 3*sqrt(7)/4)] >>> e.intersection(Ellipse(Point(100500, 0), 4, 3)) [] >>> e.intersection(Ellipse(Point(0, 0), 3, 4)) [Point2D(3, 0), Point2D(-363/175, -48*sqrt(111)/175), Point2D(-363/175, 48*sqrt(111)/175)] >>> e.intersection(Ellipse(Point(-1, 0), 3, 4)) [Point2D(-17/5, -12/5), Point2D(-17/5, 12/5), Point2D(7/5, -12/5), Point2D(7/5, 12/5)] - See also 
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is_tangent(o)[source]¶
- Is \(o\) tangent to the ellipse? - Parameters
- o : GeometryEntity - An Ellipse, LinearEntity or Polygon 
- Returns
- is_tangent: boolean - True if o is tangent to the ellipse, False otherwise. 
- Raises
- NotImplementedError - When the wrong type of argument is supplied. 
 - Examples - >>> from sympy import Point, Ellipse, Line >>> p0, p1, p2 = Point(0, 0), Point(3, 0), Point(3, 3) >>> e1 = Ellipse(p0, 3, 2) >>> l1 = Line(p1, p2) >>> e1.is_tangent(l1) True - See also 
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property major¶
- Longer axis of the ellipse (if it can be determined) else hradius. - Returns
- major : number or expression 
 - Examples - >>> from sympy import Point, Ellipse, Symbol >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.major 3 - >>> a = Symbol('a') >>> b = Symbol('b') >>> Ellipse(p1, a, b).major a >>> Ellipse(p1, b, a).major b - >>> m = Symbol('m') >>> M = m + 1 >>> Ellipse(p1, m, M).major m + 1 
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property minor¶
- Shorter axis of the ellipse (if it can be determined) else vradius. - Returns
- minor : number or expression 
 - Examples - >>> from sympy import Point, Ellipse, Symbol >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.minor 1 - >>> a = Symbol('a') >>> b = Symbol('b') >>> Ellipse(p1, a, b).minor b >>> Ellipse(p1, b, a).minor a - >>> m = Symbol('m') >>> M = m + 1 >>> Ellipse(p1, m, M).minor m 
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normal_lines(p, prec=None)[source]¶
- Normal lines between \(p\) and the ellipse. - Parameters
- p : Point 
- Returns
- normal_lines : list with 1, 2 or 4 Lines 
 - Examples - >>> from sympy import Line, Point, Ellipse >>> e = Ellipse((0, 0), 2, 3) >>> c = e.center >>> e.normal_lines(c + Point(1, 0)) [Line2D(Point2D(0, 0), Point2D(1, 0))] >>> e.normal_lines(c) [Line2D(Point2D(0, 0), Point2D(0, 1)), Line2D(Point2D(0, 0), Point2D(1, 0))] - Off-axis points require the solution of a quartic equation. This often leads to very large expressions that may be of little practical use. An approximate solution of \(prec\) digits can be obtained by passing in the desired value: - >>> e.normal_lines((3, 3), prec=2) [Line2D(Point2D(-0.81, -2.7), Point2D(0.19, -1.2)), Line2D(Point2D(1.5, -2.0), Point2D(2.5, -2.7))] - Whereas the above solution has an operation count of 12, the exact solution has an operation count of 2020. 
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property periapsis¶
- The periapsis of the ellipse. - The shortest distance between the focus and the contour. - Returns
- periapsis : number 
 - Examples - >>> from sympy import Point, Ellipse >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.periapsis 3 - 2*sqrt(2) - See also - apoapsis
- Returns greatest distance between focus and contour 
 
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plot_interval(parameter='t')[source]¶
- The plot interval for the default geometric plot of the Ellipse. - Parameters
- parameter : str, optional - Default value is ‘t’. 
- Returns
- plot_interval : list - [parameter, lower_bound, upper_bound] 
 - Examples - >>> from sympy import Point, Ellipse >>> e1 = Ellipse(Point(0, 0), 3, 2) >>> e1.plot_interval() [t, -pi, pi] 
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polar_second_moment_of_area()[source]¶
- Returns the polar second moment of area of an Ellipse - It is a constituent of the second moment of area, linked through the perpendicular axis theorem. While the planar second moment of area describes an object’s resistance to deflection (bending) when subjected to a force applied to a plane parallel to the central axis, the polar second moment of area describes an object’s resistance to deflection when subjected to a moment applied in a plane perpendicular to the object’s central axis (i.e. parallel to the cross-section) - Examples - >>> from sympy import symbols, Circle, Ellipse >>> c = Circle((5, 5), 4) >>> c.polar_second_moment_of_area() 128*pi >>> a, b = symbols('a, b') >>> e = Ellipse((0, 0), a, b) >>> e.polar_second_moment_of_area() pi*a**3*b/4 + pi*a*b**3/4 - References 
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random_point(seed=None)[source]¶
- A random point on the ellipse. - Returns
- point : Point 
 - Examples - >>> from sympy import Point, Ellipse, Segment >>> e1 = Ellipse(Point(0, 0), 3, 2) >>> e1.random_point() # gives some random point Point2D(...) >>> p1 = e1.random_point(seed=0); p1.n(2) Point2D(2.1, 1.4) - Notes - When creating a random point, one may simply replace the parameter with a random number. When doing so, however, the random number should be made a Rational or else the point may not test as being in the ellipse: - >>> from sympy.abc import t >>> from sympy import Rational >>> arb = e1.arbitrary_point(t); arb Point2D(3*cos(t), 2*sin(t)) >>> arb.subs(t, .1) in e1 False >>> arb.subs(t, Rational(.1)) in e1 True >>> arb.subs(t, Rational('.1')) in e1 True 
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reflect(line)[source]¶
- Override GeometryEntity.reflect since the radius is not a GeometryEntity. - Examples - >>> from sympy import Circle, Line >>> Circle((0, 1), 1).reflect(Line((0, 0), (1, 1))) Circle(Point2D(1, 0), -1) >>> from sympy import Ellipse, Line, Point >>> Ellipse(Point(3, 4), 1, 3).reflect(Line(Point(0, -4), Point(5, 0))) Traceback (most recent call last): ... NotImplementedError: General Ellipse is not supported but the equation of the reflected Ellipse is given by the zeros of: f(x, y) = (9*x/41 + 40*y/41 + 37/41)**2 + (40*x/123 - 3*y/41 - 364/123)**2 - 1 - Notes - Until the general ellipse (with no axis parallel to the x-axis) is supported a NotImplemented error is raised and the equation whose zeros define the rotated ellipse is given. 
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rotate(angle=0, pt=None)[source]¶
- Rotate - angleradians counterclockwise about Point- pt.- Note: since the general ellipse is not supported, only rotations that are integer multiples of pi/2 are allowed. - Examples - >>> from sympy import Ellipse, pi >>> Ellipse((1, 0), 2, 1).rotate(pi/2) Ellipse(Point2D(0, 1), 1, 2) >>> Ellipse((1, 0), 2, 1).rotate(pi) Ellipse(Point2D(-1, 0), 2, 1) 
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scale(x=1, y=1, pt=None)[source]¶
- Override GeometryEntity.scale since it is the major and minor axes which must be scaled and they are not GeometryEntities. - Examples - >>> from sympy import Ellipse >>> Ellipse((0, 0), 2, 1).scale(2, 4) Circle(Point2D(0, 0), 4) >>> Ellipse((0, 0), 2, 1).scale(2) Ellipse(Point2D(0, 0), 4, 1) 
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second_moment_of_area(point=None)[source]¶
- Returns the second moment and product moment area of an ellipse. - Parameters
- point : Point, two-tuple of sympifiable objects, or None(default=None) - point is the point about which second moment of area is to be found. If “point=None” it will be calculated about the axis passing through the centroid of the ellipse. 
- Returns
- I_xx, I_yy, I_xy : number or sympy expression - I_xx, I_yy are second moment of area of an ellise. I_xy is product moment of area of an ellipse. 
 - Examples - >>> from sympy import Point, Ellipse >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.second_moment_of_area() (3*pi/4, 27*pi/4, 0) - References - https://en.wikipedia.org/wiki/List_of_second_moments_of_area 
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section_modulus(point=None)[source]¶
- Returns a tuple with the section modulus of an ellipse - Section modulus is a geometric property of an ellipse defined as the ratio of second moment of area to the distance of the extreme end of the ellipse from the centroidal axis. - Parameters
- point : Point, two-tuple of sympifyable objects, or None(default=None) - point is the point at which section modulus is to be found. If “point=None” section modulus will be calculated for the point farthest from the centroidal axis of the ellipse. 
- Returns
- S_x, S_y: numbers or SymPy expressions - S_x is the section modulus with respect to the x-axis S_y is the section modulus with respect to the y-axis A negetive sign indicates that the section modulus is determined for a point below the centroidal axis. 
 - Examples - >>> from sympy import Symbol, Ellipse, Circle, Point2D >>> d = Symbol('d', positive=True) >>> c = Circle((0, 0), d/2) >>> c.section_modulus() (pi*d**3/32, pi*d**3/32) >>> e = Ellipse(Point2D(0, 0), 2, 4) >>> e.section_modulus() (8*pi, 4*pi) - References 
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property semilatus_rectum¶
- Calculates the semi-latus rectum of the Ellipse. - Semi-latus rectum is defined as one half of the the chord through a focus parallel to the conic section directrix of a conic section. - Returns
- semilatus_rectum : number 
 - Examples - >>> from sympy import Point, Ellipse >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.semilatus_rectum 1/3 - See also - References - [1] http://mathworld.wolfram.com/SemilatusRectum.html [2] https://en.wikipedia.org/wiki/Ellipse#Semi-latus_rectum 
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tangent_lines(p)[source]¶
- Tangent lines between \(p\) and the ellipse. - If \(p\) is on the ellipse, returns the tangent line through point \(p\). Otherwise, returns the tangent line(s) from \(p\) to the ellipse, or None if no tangent line is possible (e.g., \(p\) inside ellipse). - Parameters
- p : Point 
- Returns
- tangent_lines : list with 1 or 2 Lines 
- Raises
- NotImplementedError - Can only find tangent lines for a point, \(p\), on the ellipse. 
 - Examples - >>> from sympy import Point, Ellipse >>> e1 = Ellipse(Point(0, 0), 3, 2) >>> e1.tangent_lines(Point(3, 0)) [Line2D(Point2D(3, 0), Point2D(3, -12))] 
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property vradius¶
- The vertical radius of the ellipse. - Returns
- vradius : number 
 - Examples - >>> from sympy import Point, Ellipse >>> p1 = Point(0, 0) >>> e1 = Ellipse(p1, 3, 1) >>> e1.vradius 1 
 
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class sympy.geometry.ellipse.Circle(*args, **kwargs)[source]¶
- A circle in space. - Constructed simply from a center and a radius, from three non-collinear points, or the equation of a circle. - Parameters
- center : Point - radius : number or sympy expression - points : sequence of three Points - equation : equation of a circle 
- Raises
- GeometryError - When the given equation is not that of a circle. When trying to construct circle from incorrect parameters. 
 - Examples - >>> from sympy import Eq >>> from sympy.geometry import Point, Circle >>> from sympy.abc import x, y, a, b - A circle constructed from a center and radius: - >>> c1 = Circle(Point(0, 0), 5) >>> c1.hradius, c1.vradius, c1.radius (5, 5, 5) - A circle constructed from three points: - >>> c2 = Circle(Point(0, 0), Point(1, 1), Point(1, 0)) >>> c2.hradius, c2.vradius, c2.radius, c2.center (sqrt(2)/2, sqrt(2)/2, sqrt(2)/2, Point2D(1/2, 1/2)) - A circle can be constructed from an equation in the form \(a*x**2 + by**2 + gx + hy + c = 0\), too: - >>> Circle(x**2 + y**2 - 25) Circle(Point2D(0, 0), 5) - If the variables corresponding to x and y are named something else, their name or symbol can be supplied: - >>> Circle(Eq(a**2 + b**2, 25), x='a', y=b) Circle(Point2D(0, 0), 5) - See also - Attributes - radius (synonymous with hradius, vradius, major and minor) - circumference - equation - 
property circumference¶
- The circumference of the circle. - Returns
- circumference : number or SymPy expression 
 - Examples - >>> from sympy import Point, Circle >>> c1 = Circle(Point(3, 4), 6) >>> c1.circumference 12*pi 
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equation(x='x', y='y')[source]¶
- The equation of the circle. - Parameters
- x : str or Symbol, optional - Default value is ‘x’. - y : str or Symbol, optional - Default value is ‘y’. 
- Returns
- equation : SymPy expression 
 - Examples - >>> from sympy import Point, Circle >>> c1 = Circle(Point(0, 0), 5) >>> c1.equation() x**2 + y**2 - 25 
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intersection(o)[source]¶
- The intersection of this circle with another geometrical entity. - Parameters
- o : GeometryEntity 
- Returns
- intersection : list of GeometryEntities 
 - Examples - >>> from sympy import Point, Circle, Line, Ray >>> p1, p2, p3 = Point(0, 0), Point(5, 5), Point(6, 0) >>> p4 = Point(5, 0) >>> c1 = Circle(p1, 5) >>> c1.intersection(p2) [] >>> c1.intersection(p4) [Point2D(5, 0)] >>> c1.intersection(Ray(p1, p2)) [Point2D(5*sqrt(2)/2, 5*sqrt(2)/2)] >>> c1.intersection(Line(p2, p3)) [] 
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property radius¶
- The radius of the circle. - Returns
- radius : number or sympy expression 
 - Examples - >>> from sympy import Point, Circle >>> c1 = Circle(Point(3, 4), 6) >>> c1.radius 6 - See also - Ellipse.major,- Ellipse.minor,- Ellipse.hradius,- Ellipse.vradius
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reflect(line)[source]¶
- Override GeometryEntity.reflect since the radius is not a GeometryEntity. - Examples - >>> from sympy import Circle, Line >>> Circle((0, 1), 1).reflect(Line((0, 0), (1, 1))) Circle(Point2D(1, 0), -1) 
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scale(x=1, y=1, pt=None)[source]¶
- Override GeometryEntity.scale since the radius is not a GeometryEntity. - Examples - >>> from sympy import Circle >>> Circle((0, 0), 1).scale(2, 2) Circle(Point2D(0, 0), 2) >>> Circle((0, 0), 1).scale(2, 4) Ellipse(Point2D(0, 0), 2, 4) 
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property vradius¶
- This Ellipse property is an alias for the Circle’s radius. - Whereas hradius, major and minor can use Ellipse’s conventions, the vradius does not exist for a circle. It is always a positive value in order that the Circle, like Polygons, will have an area that can be positive or negative as determined by the sign of the hradius. - Examples - >>> from sympy import Point, Circle >>> c1 = Circle(Point(3, 4), 6) >>> c1.vradius 6 
 
