- Reading labels: "trapezoid", "rhombus", "quatrefoil", "oval", "ellipse", "curvilinear triangle" or "Reuleaux triangle"
- Frame of the circle inset (for presentation of ellipse)
- Isolate the trapezoid and identify it (trapezoid: Greek: trapezion - a little table).
- 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.
- Nowadays our tables don't look trapezoidal.
- Some Spanish tables have two legs but still not trapezoidal.
- The Greek table was like a Spanish table because it had two legs, yet it was more stable because the legs were inclined.
- Isolate the rhombus and identify it.
- This is a rhombus (rhombus: Greek: rhombos - magic wheel, top)
- 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.
- 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.
- He rotated the cane in the air as he walked causing this figure to spin around like a top, making a characteristic sound.
- This was part of a religious ritual.
- Isolate the quatrefoil and identify it (quatrefoil: Old French quatre - four, and foil - leaf).
- This figure has the shape of a four-leaf clover, considered a sign of good luck.
- Isolate the oval and identify it (oval: French ovale <Latin ovum> - egg).
- This figure has the shape of an egg.
- Isolate the ellipse and identify it (ellipse: Greek elleipsis - an omission or defect <elleipo - to leave out>).
- What has been left out?
- Think of the ideal figure, the circle.
- Place the inset of the ellipse in the circle frame and it is easy to what is missing.
- This is also the shape of the path that the earth follows around the sun.
- Isolate the Reuleaux triangle and identify it (curvilinear: Latin curvus - curved, and linear - a line).
- This triangle has three sides which are curved lines.
- It is named after a man name Reuleaux who discovered the properties of this shape.
- He found that a drill bit made in this shape will make square holes.
- 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.