Plane Geometry: Open Problems, High School, College

Open Geometry Problems - Index 2

Geometry Problem 1361.
Post a solution
Triangle, Two Nine-Point Circles, Feuerbach's Circle, Euler's Circle, Congruent Angles, Sketch, iPad Apps.

Geometry Problem 1351.
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Two Tangential or Circumscribed Quadrilaterals, Midpoints, Perpendiculars.

Geometry Problem 1345
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Three Equilateral Triangles, Center, Area, Common Vertex.

Geometry Problem 1325.
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Octagons, Midpoints, Squares, Mobile Apps, iPad.

Geometry Problem 1316.
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Triangle, Incircle, Tangent, Chord, Midpoint, Sum of two Segments, Congruence.

Geometry Problem 1282.
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Three Squares, Common Vertex, Midpoint, Perpendicular, 90 Degrees.

Geometry Problem 1253.
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Triangle, Orthocenter, Circle, Circumcircle, Altitude, Perpendicular, 90 Degree, Concurrency.

Geometry Problem 1238
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Square, Equilateral Triangle, Metric Relations. Mobile Apps.

Geometry Problem 1233
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Triangle, Euler Line, Orthic Axis, Perpendicular, 90 Degrees, Orthic Triangle.

Geometry Problem 1212
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Equilateral Triangle, Equilateral Hexagon, Concurrent Lines.

Geometry Problem 1210
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Circle, Tangent Line, Secant, Chord, Collinear Points.

Geometry Problem 1176
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Cyclic Quadrilateral, Diagonals, Six Diameters, Circles, Collinear Points, Concurrent Lines.

Geometry Problem 1175: Six Tangential or Circumscribed Quadrilaterals Theorem
Post a solution

Geometry Problem 1168
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Construction of the Inscribed Circle of the Arbelos, Semicircles, Diameter, Circle, Triangle, Circumcircle, Tangent.

Geometry Problem 1143.
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Triangle, Circumcircle, Tangent Line, Reflection of a Point over a Line, Tangent Circles, Collinear Points.

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