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		Four lines intersect, 
Sides, angles, shapes perplex, 
		Quadrilateral quests.  | 
    	
    
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		Parallelograms Index.  
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		Word Cloud of Quadrilateral. 
		Visual Summary.  | 
    
	
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				Square.  | 
    
	
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		Area of a Square Index.  
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				Rectangle. Theorems and Problems Index.  | 
    
	
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						Rhombus.
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						Trapezoids.
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		Median of a Trapezoid, Theorems and Problems. 
		Index. 
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		Cyclic Quadrilateral. 
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		Tangential or Circumscribed Quadrilateral 
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					Kite Index. 
					 
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		Complete Quadrilateral Index. 
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        Equilic Quadrilateral. 
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		Triangle and Squares. 21 theorems. Visual 
		illustrations.  | 
    
    
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      	van Aubel's Theorem. 
		Quadrilateral with Squares. Proof with animation for Tablets, iPad, 
		Nexus, Galaxy.  | 
    
    
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			Golden Rectangles.  | 
    
    
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		Ptolemy's Theorem. 
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		Tangential or Circumscribed Quadrilateral: Diagonals, Inradii Theorem.  | 
    
    
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		Tangential or Circumscribed Quadrilateral: Pitot Theorem.  | 
    
    
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	  Geometry Problem 1599: Four Equal Squares, One Right Triangle: What’s the Ratio?: A STEM Geometry Challenge  | 
      
    
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	  Geometry Problem 1596: Triangle Projections: Unraveling the DE Projection with Equal Angles!: A STEM Geometry Challenge  | 
      
      
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      Geometry Problem 1592: A Semicircle Challenge for Mental Clarity Involving Radii, Perpendiculars, Midpoint  | 
      
      
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      Geometry Problem 1591: Unravel Quadrilateral ABCD with Three Congruent Sides and Proportional Angles to Find Angle D.  | 
      
      
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      Geometry Problem 1587: 
       Uncover the Elegance of Triangle BGH's Area in Trapezoid ABCD.  | 
      
      
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      Geometry Problem 1586: 
       Unveiling a Unique Area Relationship in Three Equilateral Triangles  | 
      
      
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      Geometry Problem 1583: 
       Prove Lines CK and BL are Parallel.  | 
      
      
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      Geometry Problem 1581: 
       Prove the Angle Bisection in a Cyclic Quadrilateral.  | 
      
      
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      Geometry Problem 1582: 
       Prove That Angles AFD and AEF Are Equal in This Secant Problem.  | 
      
      
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      Geometry Problem 1578: 
       Find the Area of a Bicentric Quadrilateral with Perpendicular Extensions of Opposite Sides!.  | 
      
      
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      Geometry Problem 1570: 
      Calculating BE in Overlapping Squares: A High School and College Geometry Challenge.  | 
      
      
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      Geometry Problem 1569: 
      Prove a Relationship: EG Equals the Incircle Diameter in Triangle ABC with Square CDEF.  | 
      
      
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      Geometry Problem 1568: 
      Concyclicity of Points B, D , H, J in a Triangle ABC with an Incircle and a Tangent Circle.  | 
      
	  
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      Geometry Problem 1567: 
      Finding Tangent Distances in a Circumscribed Isosceles Trapezoid.  | 
      
      
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      Geometry Problem 1564: 
      Find the Area of Quadrilateral BGDJ in a Right Triangle involving the Altitude, Angle bisectors, and Midpoints.  | 
      
      
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      Geometry Problem 1560: 
      Trapezoid ABCD: Unlocking Angle Secrets at G and H.  | 
      
      
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      Geometry Problem 1543: Calculating the Area of Quadrilateral ABED in a Square with a Side Length of 20 and an Intersecting Arc.  | 
      
      
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      Geometry Problem 1538: Unlocking the Secrets of Triangular Geometry: Solve for the Area of a Quadrilateral Using External Squares and a Segment Length.  | 
      
      
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      Geometry Problem 1537 Challenge: Can You Solve for the Missing Area in a Parallelogram using Midpoints and Intersection Points?.  | 
      
      
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      Geometry 
	  Problem 1536: Discover the Power of Midpoints: Solving for Missing Areas in Quadrilaterals.  | 
      
      
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      Geometry 
	  Problem 1508. 
  	  Understanding Triangle Geometry: Isosceles, Equilateral, Quadrilateral, Angular. Difficulty Level: High School.  | 
      
      
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      Geometry 
	  Problem 1502. 
  	  Right Triangle, Incircle, Inradius, Geometric Mean of 2 Inradii, Angle Bisector, Perpendicular, Tangential Quadrilateral.  | 
      
      
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      Geometry 
	  Problem 1501. 
  	  Square, Exterior Point, Congruent Angles, Segment, Measurement.  | 
      
      
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      Dynamic Geometry 1481. 
  	  Five Tangential or Circumscribed Quadrilaterals, Pitot Theorem, Congruence, Step-by-step Illustration. GeoGebra, 
	  iPad.  | 
      
      
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      Dynamic Geometry 1470. 
  	  Tangential Quadrilateral, Incircles, Tangent, 
	  Parallel, Rhombus, Step-by-step Illustration.  | 
      
      
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      Geometry Problem 1467. 
  	Square, Rectangle, Triangle, Area.  | 
      
      
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      Geometry Problem 1466. 
  	Tangential Quadrilateral, Newton Line, Incenter, Midpoint, Diagonal, Collinear Points. 
	  Step-by-step Illustration using GeoGebra.  | 
      
      
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      Geometry Problem 1465. 
  	Tangential Quadrilateral, Incenter, Inscribed Circle, Equal Sum of Areas. 
	  Step-by-step Illustration using GeoGebra.  | 
      
      
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      Geometry Problem 1464. 
  	Quadrilateral, Interior Point, Midpoint of Sides, Equal Sum of Areas. 
	  Step-by-step Illustration using GeoGebra.  | 
      
      
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      Geometry Problem 1463. 
  	Parallelogram, Interior Point, Opposite Triangles with Equal Sum of Areas. 
	  Step-by-step Illustration using GeoGebra.  | 
      
      
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      Geometry Problem 1462. 
  	Newton-Line, Newton-Gauss Line, Complete Quadrilateral, Midpoints of Sides and Diagonals, 
	  Collinear Points.  | 
      
      
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      Geometry Problem 1461. 
  	Quadrilateral, Triangle, Angles, 30-60 Degree, Congruence, Auxiliary Lines.  | 
      
      
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      Dynamic Geometry Problem 1445. 
	  Van Aubel's theorem, Quadrilateral and Four Squares, Centers. Step-by-step animation using GeoGebra.  | 
      
      
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      Geometry Problem 1435. 
	  Circle, Diameter, Inscribed Circles, Circular Sector, Parallelogram, Parallel Lines, Tangency Points, 
	  Poster, Typography, iPad Apps.  | 
      
      
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      Geometry Problem 1428. Intersecting Circles, Tangent Line, Triangle, Square, Area.  | 
      
      
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      Geometry Problem 1426. Two Squares, Collinear Points, Triangle, Quadrilateral, Sum of the Areas.  | 
      
      
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      Geometry Problem 1424. Triangle, Parallelogram, Trapezoid, Area, Diagonal, Measurement.  | 
      
      
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      Geometry Problem 1422. Triangle, Transversal, Cevian, Area, 
	  Quadrilateral, Measurement.  | 
      
      
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      Geometry Problem 1403. Quadrilateral, 90 Degree Angle, Perpendicular, Congruence.  | 
      
      
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			Geometry Problem 1356. 
			Quadrilateral, Triangle, Angle, 30 Degrees, Congruence.  | 
      
      
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					Problem 1334. Square, Kite, Sum of Segments. 
					 
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		Geometry Problem 1324. 
 Quadrilateral, Diagonal, 45 Degrees, Angle Bisector, Isosceles Triangle, Congruence.  | 
      
      
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		Geometry Problem 1308. 
		 Quadrilateral, Diagonal, Triangle, Incircle, Tangent Line, Sides, Measurement.  | 
      
      
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		Geometry Problem 1286. 
		 Triangle, Quadrilateral, 60, 135, 105 Degree Angles, Congruence, Measurement.  | 
      
      
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		Geometry Problem 1285. 
		 Triangle, Quadrilateral, 60, 150, 90 Degree Angles, Congruence, Measurement.  | 
      
	
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