Triangles
From wikisori
Contents
Age
6-9.
Materials
- Reading labels - "scalene triangle", "isosceles triangle", "equilateral triangle", "right-angled triangle", "obtuse- angled triangle", "acute-angled triangle"
Preparation
Presentation
- Take out the first triangle in the first row.
- Invite the child to identify the three sides and observe whether the sides are alike or different.
- All three sides are different, this is a scalene triangle.
- Relate the story of the farmer and the ladder he used to pick fruit from his trees.
- Unlike the ladders we use today, the rungs of this ladder were all different lengths.
- These ladders are still used today in lesser developed countries.
- Just as all the rungs are different lengths, the sides of this triangle are all different lengths (scalene: Latin scala, usually plural scalae - ladder, flight of steps or Greek: skalenas - limping, uneven).
- Isolate the second triangle in the first row.
- Invite the child to carefully observe its sides - two are alike.
- This is an isosceles triangle (isosceles: Greek isos - equal, and sceles - legs; thus having equal legs).
- Here it means two equal legs, or sides.
- Isolate the third triangle.
- By observing and turning the inset in its frame, the child sees that all of the sides are the same.
- This is an equilateral triangle (equilateral: Latin aequus - equal, and latus, lateris - a side; thus having equal sides).
- Place the three insets on the table and do a three period lesson.
- Isolate the first triangle in the second row.
- Identify the right angle.
- This is a right angle, it is erect.
- This is a right-angled triangle.
- How many right angles does it have? Only one.
- Isolate the second triangle.
- Identify the obtuse angle.
- Obtuse means dull.
- This is an obtuse-angled triangle.
- Count the obtuse angles... only one.
- Isolate the third triangle.
- All of these angles are smaller than the right angle.
- They are acute angles.
- Acute means sharp, pointed.
- Feel how it is sharper than the right or obtuse angles.
- This is an acute-angled triangle.
- How many acute angles does it have? Three.
- Bring out the three triangles and review the first period.
- The triangle must have one right angle to be a right-angled triangle... and so on.
- Second and third periods follow.
- Give the child the reading labels.
Control Of Error
Points Of Interest
Purpose
Variation
Links
Handouts/Attachments