Activity Overview
Students use the Cabri Geometry II Plus software to investigate the geometric property of dilation. They vary the scale factor and examine the effect on the dilation of a triangle.
Before the Activity
Download the Cabri Geometry™ software on the computer
See the attached FIG file for details of this activity
During the Activity
Follow the Activity procedure:
Move Point K along the line
Note that for positive values of K, the triangle maintains its shape, but changes its size with respect to point O
Note that for K = 1, the two triangles coincide
Note that for K = 0, the dilated triangle coincides with point O
Observe that for negative values of the scale factor K, the dilated image gets inverted, and increases in size as the K value decreases
Understand that at K = 0.50, the sides of the dilated triangle will be half the length of sides of the original triangle, while the angles remain same
After the Activity
Review student results:
As a class, discuss questions that appeared to be more challenging
Re-teach concepts as necessary