Using Tools to Make Perpendicular Lines

Yesterday students learned about parallel and perpendicular lines, and how to draw them.  The tool we chose to start with was a triangular ruler, that has a 90° angle incorporated in its structure.  This led us to today's goal:

With a bag of different measuring tools in front of them, students first choose the one we know and demonstrated how to use it to create perpendicular lines.  Then, from the remaining tools left on their desks they needed to choose on that they thought they could use to create perpendicular lines.

After some discussion, and trying out one tool which we deemed would not work to accurately create a perpendicular line, they decided that we could use a protractor to help us in this endeavour.  Through a class demonstration, the students agreed that indeed this would work.  So then we set out to practice creating perpendicular lines alternating between the two measuring tools.

Making Lines

Using triangle rulers, students practiced making parallel and perpendicular lines today.  It's nice to start with graph paper to help ensure that our lines are straight and that we do create 90° angles.  When we leave the graph paper, our triangle rulers will definitely help as will using a protractor.  It's amazing how previous unit concepts return to be applied again. ;)

Parallel and Perpendicular Lines

Our next mini geometry unit is about lines; parallel and perpendicular lines to be exact.  Today students first explored concepts and shared what they observed about two separate images of lines.  From doing so and our class discussion, we discovered the properties of parallel and perpendicular lines.  Also, we found that moving the turning or rotating the image did not change the properties of the lines.

Parallel Lines
1. Made by two straight lines / line segments
2. The lines never meet.
3. The distance between the lines remains the same at all points.

Perpendicular Lines
1.  Made by two straight lines / lines segments
2.  The lines meet.
3.  Where the lines meet creates a 90° angle.

After we explored this visually and through discussion, the students then used strips of paper to create parallel and perpendicular lines.  We found that using measurement tools (ie rulers and right triangle rulers) helps to ensure accuracy of our lines.