Education Technology

Got an equilateral triangle? with Cabri Jr.

Published on 06/09/2008

Activity Overview

Using the Compass tool in Cabri Jr., students will construct an equilateral triangle, and check the length of each side. When a vertices is moved using the Alpha hand, the triangle remains equilateral.

Before the Activity

Students need basic knowledge of selecting Cabri Jr. tools, Clear key, Alpha key to drag, etc.

During the Activity

F2 select Segment tool. After drawing one segment, clear tool. F3 select Compass tool. Select each endpoint of the segment. A circle will be displayed. (The segment is the radius of the circle created by the Compass tool) Still using the Compass tool, select each endpoint of the segment. Be sure to explain to the students to choose the endpoints in the opposite order. For example, if the first Compass circle was displayed using the left endpoint first and the right endpoint second. Then the second Compass circle needs to use the right endpoint first and the left endpoint second. F2 Point> select Intersection place a point at the intersection of the Compass circles. (NOTE?there will be two points of intersection, choose only one.) F5 Hide/Show> select Object move to each circle one at a time and hide each Compass circle. The segment and the point of intersection should be left on the screen. F2 select Triangle. Create a triangle using the two endpoints of the segment and the intersection point. F5 Measure> select D.&Length. Measure each side of the triangle. When each length is displayed, move the value near its side. Select a side or vertices of the triangle with the Alpha hand and drag. The sides maintain there equivalency.

After the Activity

For added accuracy?select the length of a side (a line under the numbers ?shimmers? when selected) hit the Plus key twice. Select the length of the second side, hit the Plus key twice. Select the length of the third side, hit the Plus key twice. Now select a side of the triangle or one of its vertices, and Alpha hand drag. They are equal to the hundredths place. Note?to remove the decimals select a displayed value and hit the Minus key. For further discussion: F5 Measure> select Angle. Measure each angle to display that the angles are each 60 degrees and the triangle is also equiangular. Take a 1to10. A 1to10 is a way to monitor the understanding of a class. Ask the students to 2nd quit Cabri Jr (or any APP), and have only a black curser on the calculator. Ask a question about their understanding of equilateral and equiangular triangles. Students place a 1 to 10 on their screen. 1 equals the need for further explanation, and 10 equals total understanding of the concept. Screen Capture in TI-Navigator. (Quick Poll can also be used for 1to10)