Triangles: Theorems and Problems 33

Interactive Orthopole of a Triangle: Using TracenPoche Dynamic Geometry Software, Online Step-by-Step construction, manipulation, and animation.

Proposed Problem 70: Squares inscribed in a triangle, Similarity.

Morley's Triangle & Center: with interactive animation and manipulation.

Schiffler Point: Four Euler Lines with interactive animation and manipulation.

Proposed Problem 69: Square inscribed in a triangle, Similarity.

Proposed Problem 68: Triangle, Incircle, Inradius, Tangent, Similarity.

Proposed Problem 67: Triangle, Circumcircle, Angles, Cyclic Quadrilateral.
 

Van Aubel's Theorem II: Triangle and Cevians.
 

Proposed Problem 66: Triangle, Excircle, Tangents, Geometric Mean.
 

Feuerbach Points and Nine-Point Circle with interactive animation, manipulation, and step-by-step construction.

Proposed Problem 65: Right Triangle, Mindpoints.

Proposed Problem 64: Triangle, Incircle, Transversal.

Machu Picchu and Sierpinski Triangle. Equilateral

Machu Picchu and Sierpinski Tunel Effect.

Proposed Problem 61: Triangle, Trisection of Sides

Proposed Problem 87. Area of Quadrilaterals and Midpoints of Diagonals.

Intouch and Extouch Triangles. Puzzle cut: 20 Piece Classic
Based on Proposed Problem 86.

Proposed Problem 86. Intouch and Extouch Triangles, Areas.

Puzzle: Marion Walter's theorem. Puzzle cut: 12 Piece ZigZag
Based on Marion Walter's theorem

Contact Triangles. Puzzle cut: 22 Piece Polygons
Based on Proposed Problem 85.

Proposed Problem 85. Contact Triangles Areas, Incircle, Excircle.

Proposed Problem 84. Contact Triangles Areas, Incircle, Excircle, Inradius, Exradius.

Proposed Problem 83. Area of the Excircle Contact Triangle, exradius, circumradius.

Proposed Problem 82. Area of the Contact Triangle, inradius, circumradius.

Proposed Problem 81. Area of a triangle, side, inradius, circumradius.

Proposed Problem 80. Area of a triangle, side, incircle, inradius.

Proposed Problem 79: Triangle. Similarity, Altitudes, Orthocenter, Incircles, Inradii.

Newton's Theorem, Newton-Gauss Line: Complete quadrilateral theorem. Using TracenPoche Dynamic Geometry Software, Online Step-by-Step construction, manipulation, and animation.