Activity Overview
Students use the Cabri™ Jr. application to draw triangles and explore properties of perpendicular bisectors of the three sides of different types of the triangles. They study the measures of angles of a triangle and understand that the sum of the measures of angles of a triangle is always 180 degrees.
Before the Activity
Install the Cabri: Jr. App on the students' graphing calculators using one of these two methods:
TI-Connect™, a TI Connectivity Cable, and the Unit-to-Unit Link Cable
TI-Navigator™ "send to class" feature
See the attached PDF file for detailed instructions for this activity
Print pages 1 - 19 from the attached PDF file for your class
During the Activity
Distribute the pages to the class.
Follow the Activity procedures:
Explore the tools and submenus accessed through the function keys
Construct a triangle and label its vertices
Measure the angles of the triangle
Construct three perpendicular bisectors on each of the sides of the triangle
Determine the point of intersection of the perpendicular bisectors
Hide the perpendicular bisectors and display only the intersection point
Make conjectures about the intersection of the perpendicular bisectors of a triangle when the triangle is acute, right, or obtuse
Draw a triangle and measure the angles
Calculate the sum of the angle measures and observe that it is 180 degrees
Move a vertex around the screen and observe that the sum does not change
After the Activity
Review student results:
As a class, discuss questions that appeared to be more challenging
Re-teach concepts as necessary