The instructor:

• Asks children to study figure A.
• Points at the word "Diagonal" and tells children "diagonal" means reaching from angle to angle.
• Tells children a diagonal divides a rectangle into two right triangles.
• Asks children to look at figure B.
• Tells children that two diagonals divide a horizontal or vertical rectangle into two acute and two obtuse triangles.
• Asks children to look at figure C.
• Tells children that two diagonals divide a square rectangle into four right triangles.
• Tells children the center is where the two diagonals cross.

The instructor:

• Asks children to the name the shapes of parts 1 and 2."
• Asks children to the name the shapes of part 3."
• Asks children to the name the shapes of part 4."
• Asks children to the name the shapes of part 5."
• Asks children to point to the center of the square rectangle.
• Asks children to point to the center of the horizontal rectangle.

Children complete the following drill work:

1. Draw a horizontal rectangle and divide it into two right triangles.
2. Draw a vertical rectangle and divide it into two right triangles.
3. Draw a square rectangle and divide it into two right triangles.
4. Draw a square rectangle and divide it into four right triangles.
5. Draw a horizontal rectangle and divide it into two acute triangles and two obtuse triangles

The instructor:

• Asks children to study the bottom image.
• Tells children this drawing contains sixteen large rectangles and fourteen large triangles.
• Asks children to find and trace the rectangles in the picture with their forefinger.

The instructor asks children the following about the bottom image:

• Where is an acute triangle?
• Where is an obtuse triangle?
• Where is a right triangle?
• What is the shape of the stone work of the bridge?
• What is the shape of the bank on the right? The bank and its reflection together?
• What is the shape of the stone abutment and the bank together?
• What is the shape of the stone abutment and its reflection?
• What is the shape of the bank and its reflection?
• What is the shape of the truss?
• What is the shape of the beam?
• What is the shape of the space under the beam?
• What is the shape of the whole drawing?
• What is the shape of the space above the roadway?
• What is the shape of the whole space below the roadway?