Presentation of the Material – Triangles

Presentation of the Material – Triangles

Materials:
Insets of the fractional parts of a triangle
Geometry charts… triangle 1,2,3,4

Presentation: Bring out the four insets. Identify the whole triangle: equilateral, whole, unit. Identify the others in the same way as before: the number of equal parts, how they were formed, the value of each resulting piece.

The same triangle was divided into two equal parts by the height. Each has the value of 1/2. the same triangle was divided into three equal parts by the angle bisectors extending to the point of intersection. Each has the value of 1/3. the same triangle was divided into four equal parts by finding the midpoints of the sides and joining them. Each has the value of 1/4.

Classify the triangles which have been formed: 1/2 – right-angled scalene triangle; 1/3 – obtuse-angled isosceles triangle; 1/4 – equilateral triangle. show chart 1.

Examine the relationship between the lines of the fractional triangles and the whole. Show charts 2,3 and 4.

Exercise: the child may construct his own charts.