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Plane Geometry: Open Problems, High School, College
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Open Geometry Problems - Index 3
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![Geometry problem 1139](../school-college/2/p1139-triangle-circumcircle-bisector-parallel-90-degrees-concurrent-1.jpg) |
Geometry Problem 1139.
Post a solution Triangle, Circumcircle, Angle Bisector, Parallel Lines, 90 Degrees, Concurrent Lines. |
![Geometry problem 1137](../school-college/2/p1137-triangle-orthocenter-circle-midpoint-collinear-1.jpg) |
Geometry Problem 1137.
Post a solution Triangle, Circumcircle, Orthocenter, Midpoint, Arc, Collinear Points, Tangent Circles. |
![Geometry problem 1134](../school-college/2/p1134-circle-tangent-circumcenter-circumcircle-triangle-1.jpg) |
Geometry Problem 1134.
Post a solution Tangent Circles, Tangent Line, Triangle, Circumcircle, Circumcenter. |
![Geometry problem 1127](../school-college/2/p1127-triangle-circumcircle-tangent-diameter-90-degrees-1.jpg) |
Geometry Problem 1127.
Post a solution Triangle, Circumcircle, Tangent, Circle, Diameter, Midpoint, Perpendicular, 90 Degrees. |
![Geometry problem 1125](../school-college/2/p1125-triangle-four-equilateral-centroid-midpoint-1.jpg) |
Geometry Problem 1125.
Post a solution Triangle, Four Equilateral Triangles, Centroid, Midpoint. |
![Geometry problem 1122](../school-college/2/p1122-triangle-orthocenter-90-degree-midpoint-collinear-math-1.jpg) |
Geometry Problem 1122.
Post a solution Triangle, 90 Degree, Perpendicular Lines, Orthocenter, Altitude, Midpoint, Collinear Points.
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![Geometry Problem 1119](../school-college/2/p1119-quadrilateral-similar-triangle-midpoint-ratio-angle-math-1.jpg) |
Geometry Problem
1119.
Post a solution Quadrilateral, Similar Triangles, Midpoints, Equal Ratio, Angles. |
![Circumscribed Quadrilateral, Angles](../problem/p724_quadrilateral_circle1.jpg) |
Geometry Problem
724.
Post
a solution
Circumscribed Quadrilateral, Circle, Angle, Incenter, Half
the Measure. |
![Geometry Problem 1105](../school-college/2/p1105-triangle-cevian-incircle-excircle-congruence-geometric-mean-math-tutor-1.jpg) |
Geometry Problem
1105.
Post a solution Triangle, Incircle, Excircle, Cevian, Tangent, Congruence, Geometric Mean. |
![Geometry Problem 1099](../school-college/1/p1099-four-circles-common-external-internal-tangent-radius-sangaku-1.jpg) |
Geometry Problem
1099.
Post a solution
Four Circles, Common External Tangent, Common Internal Tangent, Radius, Metric Relations,
Sangaku Japanese Geometry. |
![Geometry Problem 1071](../school-college/1/p1071-arbelo-circle-semicircle-perpendicular-tangent-midpoint-problem-solving-tutor-1.jpg) |
Geometry Problem
1071.
Post a solution
Arbelos, Semicircles, Diameter, Circle, Perpendicular, Common Tangent, Parallel, Collinear Points, 90 Degrees,
Midpoint. |
![Geometry Problem 1068](../school-college/1/p1068-obtuse-triangle-orthocenter-exradius-inradius-circumradius-distance-math-1.jpg) |
Geometry Problem
1068.
Post a solution
Obtuse Triangle, Orthocenter, Circumradius, Inradius, Exradii, Distance, Diameter |
![Geometry Problem 1066](../school-college/1/p1066-triangle-obtuse-orthocenter-inradius-circumradius-distance-math-1.jpg) |
Geometry Problem
1066.
Post a solution
Triangle, Obtuse Angle, Orthocenter, Circumradius R, Inradius r, Exradius
ra, Distance, Diameter. |
![Geometry Problem 1051](../school-college/1/p1051-square-triangle-circle-semicircle-arc-area-math-1.jpg) |
Geometry Problem
1051.
Post a solution
Triangle, Square, Semicircle, Arc, Area. |
![Geometry Problem 1024](../school-college/1/p1024-contact-triangle-side-incircle-product-perpendicular-online-math-1.jpg) |
Geometry Problem
1024.
Post a solution
Contact, Gergonne Triangle, Point on an arc of Incircle, Perpendicular, Distances. |
![Geometry Problem 1012](../school-college/1/p1012-equilateral-triangle-incenter-perpendicular-concurrent-math-1.jpg) |
Geometry Problem
1012.
Post a solution
Equilateral Triangle, Incenters, Inscribed Circles, Perpendicular, Concurrent Lines. |
![Geometry Problem 1008](../school-college/1/p1008-three-equal-tangent-circles-sum-lines-math-1.jpg) |
Geometry Problem
1008.
Post a solution
Three Equal Tangent Circles, Sum of Tangent Lines, Tangency Points. |
![Geometry Problem 1007](../school-college/1/p1007-hexagon-midpoint-triangle-median-centroid-concurrent-math-1.jpg) |
Geometry Problem
1007.
Post a solution
Hexagon, Midpoint, Triangle, Median, Centroid, Concurrency. |
![Geometry Problem 991](../school-college/p991-triangle-isosceles-incircle-tangent-midpoint-collinear-1.jpg) |
Geometry Problem 991.
Post a solution
Triangle, Incircle, Tangency Points, Isosceles, Midpoint, Collinearity, Congruence, Circle. |
![Geometry Problem 990](../school-college/p990-triangle-incircle-median-circle-central-angle-congruence-1.jpg) |
Geometry Problem 990.
Post a solution
Triangle, Incircle, Median, Cevian, Central Angle, Congruence, Circle, Secant, Midpoint,
Parallel. |
![Geometry Problem 988](../school-college/p988-right-triangle-cevian-30-degrees-triple-angle-1.jpg) |
Geometry Problem 988.
Post a solution
Right Triangle, Cevians, Angles, 30 Degrees, Triple Angle. |
![Geometry Problem 987](../school-college/p987-triangle-circumcircle-incenter-parallel-circle-tangent-animation-ipad-1.jpg) |
Geometry Problem 987.
Post a solution
Triangle, Circumcircle, Incenter, Chord, Parallel, Circle, Tangent. GeoGebra, HTML5 Animation for Tablets (iPad, Nexus). |
![Geometry Problem 974](../school-college/p974-cevian-triangle-reflection-concurrency-begonia-theorem-point-geogebra-1.jpg) |
Geometry Problem 974.
Post a solution
'Begonia Theorem', Cevian Triangle, Reflection of a point in a line, Concurrency of Lines. GeoGebra, HTML5 Animation for Tablets. |
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