# Activities

• • • ##### Subject Area

• Math: Geometry: Reasoning

• ##### Author 9-12

15 Minutes

• ##### Device
• TI-83 Plus Family
• TI-84 Plus
• TI-84 Plus Silver Edition
• TI-Navigator™
• ##### Software

TI-SmartView™

## Got Complements? with Cabri Jr.

#### Activity Overview

Use the Axes and Measure Angle tool to explore and calculate complementary angles.

#### Before the Activity

Students must have basic knowledge of the Cabri Jr. including: Clear button, Alpha is the Drag tool, selecting tools, etc.

#### During the Activity

F5 Hide/Show> select Axes on. Measure the angle of the first quadrant. Use the measure tool. Select a positive point on the y-axis, the origin as the vertex, and a positive point on the x-axis. Drag the 90 degrees below. This is a reference angle and proof that the original angle is 90 degrees. Create a line segment using the origin and a point in the first quadrant. Measure both angles created with the segment. Drag each value of degrees near its angle. F5 Calculate--choose one of angles' value Plus the other angle's value. Drag the endpoint of the segment created in the first quadrant. As students drag the endpoint (staying in the first quadrant), the angles measured change, and the calculation still reflects 90 degrees. One discussion, what happens to the calculation as you drag the endpoint into a different quadrant? Students can label each point to clearly define the angles. Another discussion, when do the angles become supplements? And, why don't the straight angles equal 180 degrees? The point to stress: the calculation was the sum of the two angles.

#### After the Activity

F1 New screen. Try same exercise with Supplements. Reference angle is a straight angle or the x-axis. 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 complements. 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)