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X₄₈₂¶

2nd EPPSTEIN POINT

Let S' be the outer Soddy circle and \(S_{A}\), \(S_{B}\), \(S_{C}\) the Soddy circles tangent to S. Let J_A = S'∩\(S_{A}\), E_A = \(S_{B}\)∩\(S_{C}\), and determine J_B, J_C, E_B, E_C cyclically. Then X₄₈₂ is the point of concurrence of lines J_A-to-E_A, J_B-to-E_B, J_C-to-E_C.

X₄₈₂ (2nd EPPSTEIN POINT) constructed on acute reference triangle \((a, b, c) = (5, 6, 7)\) with unit baseline AB = \(1\).¶

"""GEOMETOR construction model for X_482 = 2nd EPPSTEIN POINT."""

        from __future__ import annotations

        from pathlib import Path

        import sympy.geometry as spg
        from geometor.model import Model

        from geometor.etc.ops import (
            central_line,
            ceva_conjugate,
            construct_baseline_triangle,
            create_model,
            eval_trilinear_point,
            gergonne_point_of,
            incenter_of,
            promote_point_to_top,
        )
        from geometor.etc.render import write_center_svg


        def construct_x_00482(
            model: Model, A: spg.Point, B: spg.Point, C: spg.Point
        ) -> spg.Point:
            """Construct X_482 = 2nd EPPSTEIN POINT on reference triangle ABC."""
            X_79 = eval_trilinear_point(model, A, B, C, '1/(1 + 2*cos(A))', ID="X_79", classes=["center"])
            X_481 = eval_trilinear_point(model, A, B, C, '1 - 2*sec(A/2)*cos(B/2)*cos(C/2)', ID="X_481", classes=["center"])
            X_482 = ceva_conjugate(model, A, B, C, X_79, X_481, ID="X_482", classes=["selected", "target"])
            X_1 = incenter_of(model, A, B, C, ID="X_1", classes=["center", "incident"])
            X_7 = gergonne_point_of(model, A, B, C, ID="X_7", classes=["center", "incident"])
            central_line(model, X_1, X_7, 1, 7, incident=True)
            X_226 = eval_trilinear_point(model, A, B, C, '(csc(A))*(cos(B) + cos(C))', ID="X_226", classes=["center", "incident"])
            X_486 = eval_trilinear_point(model, A, B, C, 'sec(A +  pi  /4)', ID="X_486", classes=["center", "incident"])
            central_line(model, X_226, X_486, 226, 486, incident=True)
            return promote_point_to_top(model, X_482)


        def build_model(
            sides: tuple[float, float, float] = (5.0, 6.0, 7.0),
            show_guides: bool = False,
        ) -> Model:
            """Build a `geometor.model.Model` for X_482 on the given reference triangle."""
            model = create_model('X_482 = 2nd EPPSTEIN POINT')
            A, B, C = construct_baseline_triangle(model, *sides, show_guides=show_guides)
            construct_x_00482(model, A, B, C)
            return model


        if __name__ == "__main__":
            here = Path(__file__).resolve().parent
            model_acute = build_model((5.0, 6.0, 7.0))
            model_acute.save(str(here / "x-00482.json"))
            write_center_svg(
                model_acute,
                here / "x-00482.svg",
                subtitle="(a, b, c) = (5, 6, 7) | AB = 1",
            )
        

X482¶

X₄₈₂¶