Other Figures

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  • Reading labels: "trapezoid", "rhombus", "quatrefoil", "oval", "ellipse", "curvilinear triangle" or "Reuleaux triangle"
  • Frame of the circle inset (for presentation of ellipse)



  1. Isolate the trapezoid and identify it (trapezoid: Greek: trapezion - a little table).
  2. In order to understand why this figure has its name we must go back in time to see what a table of the Greeks looked like.
  3. Nowadays our tables don't look trapezoidal.
  4. Some Spanish tables have two legs but still not trapezoidal.
  5. The Greek table was like a Spanish table because it had two legs, yet it was more stable because the legs were inclined.
  6. Isolate the rhombus and identify it.
  7. This is a rhombus (rhombus: Greek: rhombos - magic wheel, top)
  8. In ancient Greece, in the city of Athens, during a religious procession through the streets, a priest walked along with a cane (rod) raised over his head.
  9. At the end of the cane there was a cord attached, and at the end of the cord there was a rhombus-shaped figure attached.
  10. He rotated the cane in the air as he walked causing this figure to spin around like a top, making a characteristic sound.
  11. This was part of a religious ritual.
  12. Isolate the quatrefoil and identify it (quatrefoil: Old French quatre - four, and foil - leaf).
  13. This figure has the shape of a four-leaf clover, considered a sign of good luck.
  14. Isolate the oval and identify it (oval: French ovale <Latin ovum> - egg).
  15. This figure has the shape of an egg.
  16. Isolate the ellipse and identify it (ellipse: Greek elleipsis - an omission or defect <elleipo - to leave out>).
  17. What has been left out?
  18. Think of the ideal figure, the circle.
  19. Place the inset of the ellipse in the circle frame and it is easy to what is missing.
  20. This is also the shape of the path that the earth follows around the sun.
  21. Isolate the Reuleaux triangle and identify it (curvilinear: Latin curvus - curved, and linear - a line).
  22. This triangle has three sides which are curved lines.
  23. It is named after a man name Reuleaux who discovered the properties of this shape.
  24. He found that a drill bit made in this shape will make square holes.
  25. Give three-period lesson and give the reading labels.

Control Of Error

Points Of Interest


  • Knowledge of the geometric figures and their relative exact nomenclature.