# Online Geometry: Congruence, Rotation, Translation, Reflection - Page 1

Euclid's Elements Book I, 23 Definitions. One-page visual illustration.
Euclid's Elements Book. Index

Parallelogram with Squares theorem Thébault's Theorem.

Johnson's Theorem, Intersecting circles.
HTML5 Animation

Varignon and Wittenbauer parallelograms. Quadrilateral: midpoints and trisection points of the edges.

Van Aubel's Theorem. Quadrilateral with Squares. Proof with animation.

Langley's Problem Adventitious angles. 20° isosceles triangle with animation.

Geometry Problem 1525 and a Thematic Poem.
Unveiling the Secrets of an Equilateral Triangle in Right Triangle Geometry: Finding the Midpoint Distance between Segments.

Geometry Problem 1524 and a Thematic Poem.
Unlock the Mystery of Parallelograms: Discover the Length of Segment between the Intersecting Angle Bisectors.

Geometry Problem 1523 and a Thematic Poem.
Discover How to Calculate the Length of the Altitude in an Isosceles Triangle - Get Expert Geometry Tips Now! .

Geometry Problem 1513 and a Thematic Poem.
Solving the base in a Right Trapezoid with Double Angle and Sum of Two Sides. Difficulty Level: High School.

Geometry Problem 1511 and Poem.
Finding the Altitude of an Isosceles Triangle Using Distances from a Point on the Extension of the Base. Difficulty Level: High School.

Geometry Problem 1510 and Poem.
Congruence of Triangles, Perimeter, Measurement. Difficulty Level: High School.

Geometry Problem 1509 and Poem.
Congruence of Triangles in a Trapezoid and a Square, Measurement. Difficulty Level: High School.

Geometry Problem 1503.
Triangle, Incircle, Tangent, Congruence, Perpendicular.

Geometry Problem 1501.
Square, Exterior Point, Congruent Angles, Segment, Measurement.

Geometry Problem 1499.
Triangle, Angles, Cevian, Congruence, Isosceles, Equilateral, Auxiliary Construction.

Geometry Problem 1496.
Triangle, Congruence, Isosceles, Double Angle, 30 Degrees.

Geometry Problem 1461.
Quadrilateral, Triangle, Angles, 30-60 Degree, Congruence, Auxiliary Lines.

Dynamic Geometry Problem 1447.
Outer Vecten Point. Step-by-step illustration using GeoGebra.

Dynamic Geometry Problem 1445.
Van Aubel's theorem, Quadrilateral and Four Squares, Centers. Step-by-step animation using GeoGebra.

Geometry Problem 1431.
Triangle, Circumcircle, Parallel Chord, Apollonius, LLC, Congruent Angles, Poster, Conformal Mapping.

Geometry Problem 1429.
Triangle, Median, 15-30 degree, Angle, Congruence.

Geometry Problem 1428.
Intersecting Circles, Tangent Line, Triangle, Square, Area.

Geometry Problem 1406.
Four Congruent Circles, Measurement, Metric Relations, Sum of the Squares.

Geometry Problem 1405.
Four Congruent Circles, Congruent Chords.

Geometry Problem 1404.
Three Circles, Center, Intersecting Points, Collinearity, Congruence.

Geometry Problem 1403.
Quadrilateral, 90 Degree Angle, Perpendicular, Congruence.

Geometry Problem 1401.
Right Triangle with three circles on the sides, Isosceles, Diameter, Center, Tangent, Congruence.

Geometry Problem 1389.
Triangle, 40-120-20 degree, Angle, Congruence.

Geometry Problem 1388.
Triangle 40-60-80 degree, Incenter, Congruence.

Geometry Problem 1382.

Geometry Problem 1380.
Common Internal Tangents. Circles, Secant, Congruent Chords.

Geometry Problem 1379.
Common External Tangents. Circles, Secant, Congruent Chords.

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

Geometry Problem 1359.
Triangle, Circumcircle, Congruent Angles, Midpoints.

Geometry Problem 1356.
Quadrilateral, Triangle, Angle, 30 Degrees, Congruence.

Geometry Problem 1353.
Tangent Circles, Perpendicular Diameters, Congruence, 30 Degrees.

Geometry Problem 1349.
Three Squares, 90 Degrees, Perpendicular Lines, Diagonal. Math Infographic.

Geometry Problem 1348.
Three Concentric Circles, Equilateral Triangle, Perpendicular Bisector, Congruence.

Geometry Problem 1347.
Triangle, Angle Bisector, Congruence, Circumcircle, Tangent, Equilateral Triangle.

Geometry Problem 1329.
Two Squares Side by Side, Parallel, Perpendicular, 90 Degrees, Congruence.

Geometry Problem 1328.
Two Squares Side by Side, Perpendicular, 90 Degrees, Congruence.

Geometry Problem 1317.
Triangle, Excircle, Chord, Tangent, Midpoint, Arc, Sum of two Segments, Congruence.

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

Geometry Problem 1315.
Triangle, Incircle, Tangent, Chord, Circle, Congruence.

Geometry Problem 1314.
Equilateral Triangle, Incircle, Inscribed Circle, Tangent, Congruence.

Geometry Problem 1313.
Regular Decagon, Pentadecagon, Equilateral Triangle, Congruence.

Geometry Problem 1304.
Triangle, 120 Degrees, Angle Bisector, Measurement.

Geometry Problem 1303.
Triangle, 60 Degrees, Angle Bisector, Measurement.

Geometry Problem 1302.
Triangle, Median, Midpoint, Circles, Diameters, Congruence.

Geometry Problem 1295.
Right Triangle, Incenter, Incircle, Excenter, Excircle, Congruence, Angle.

Geometry Problem 1293.
Triangle, Altitudes, Two Squares, Center, Concurrent Lines, Midpoint.

Geometry Problem 1291.
Three Squares, Collinear Vertices, Midpoint, Congruence.

Geometry Problem 1287.
Triangle, 40-100-40 Degrees, Congruence, Area, Metric Relations, Measurement.

Geometry Problem 1286.
Triangle, Quadrilateral, 60, 135, 105 Degree Angles, Congruence, Measurement.

Geometry Problem 1285.
Triangle, Quadrilateral, 60, 150, 90 Degree Angles, Congruence, Measurement.

Geometry Problem 1284.
Two Equilateral Triangle, Midpoint, Congruence.

Geometry Problem 1278.
Square, 3-4-5 Right Triangle, Midpoint.

Geometry Problem 1272.
Isosceles Triangle, Median, Midpoint, Perpendicular, 90 Degrees, Angles, Congruence.

Geometry Problem 1250.
Cyclic or Inscribed Quadrilateral, Circle, Diameter, Congruence.

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

Geometry Problem 1237
IMO 2016, Problem 1, Triangle, Congruence, Parallel Lines, Midpoint, Concurrency.

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HomeGeometry | Congruence | Email | by Antonio Gutierrez
Last updated: Aug 11, 2024