Education Technology

# Activities

• ##### Subject Area

• Math: Geometry: Points, Lines and Angles

6-8
9-12

60 Minutes

• ##### Device
• TI-83 Plus Family
• TI-84 Plus
• TI-84 Plus Silver Edition

TI Connect™

• ##### Accessories

TI Connectivity Cable

• ##### Other Materials
The following equipment is required for this activity:
• TI-Presenter™

• LCD Projector
• Two screens

## Lines in the Plane

#### Activity Overview

In this activity, students create a slope triangle and understand the concepts of slope and the equation of lines. They realize that slope is constant at all points along a fixed line. They also explore the slopes of parallel and perpendicular lines.

#### 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 - 7 from the attached PDF file for your class
• #### During the Activity

Distribute the pages to your class.

• Draw a horizontal segment and construct a point on the y-axis
• With the length of the segment as radius, draw a circle with the point as the center
• Enlarge the circle so that the point in the first quadrant is in the upper right corner of the screen
• Construct a point on the circle in the first quadrant and draw a line connecting it to the center
• Hide the circle and the segment, and construct 2 points, A and C, on the line
• Draw a perpendicular from C to the X-axis, and a perpendicular from A to the Y-axis
• Label the intersection of the perpendiculars as B
• Hide the perpendicular lines, draw segments AB and BC, measure their lengths, and compute the ratio BC/AB
• Drag A or C along the line and observe the variation in the value of the ratio
• Display the equation of the line and its slope
• Rotate the line around the y-intercept and examine the relationship between the slope and the equation
• Observe the changes in the equation as the y-intercept is changed
• Explore the slopes of parallel and perpendicular lines and determine the products of the slopes of perpendicular lines
• #### After the Activity

Review student results:

• As a class, discuss questions that appeared to be more challenging
• Re-teach concepts as necessary