Drawing Triangles (Part 1)
Warmup
The triangle shown above are similar triangles. can you explain why?
Activity #1
To Construct an Equilateral Triangle.
Follow the instructions below to construct an Equilateral Triangle. If you get confused, pause and watch the video below.
- Click the Regular Polygon icon.
- Click on the screen in two places and a dialog box pops up.
- Type 3 and press Enter on your key board.
- An equilateral triangle will be created.
- Click on the Distance or Length tool.
- Click each side of the triangle and the lengths of the sides will be labeled.
- Click on the Angle tool.
- Click on the triangle and all the angles will be marked.
- Play around with the vertices of the triangle to confirm that the side lengths and angles remain the same.
Activity #2
To Construct an Isosceles Triangle.
- Follow the instructions below to construct an isosceles Triangle. If you get confused, pause and watch the video below.
Activity #3
How to construct a triangle given two angle measures and one side length.
- Use Angle 1 and Angle 2 sliders to choose two acute angles.
- Use slide AB to choose a side length. Side length CA is not constrained.
- So grab point C and slide it up or down to create a triangle. B is just a point, so go slowly as you approach it. When the line snaps on B, a triangle will be created as you’ll see all three sides and angles.
Challenge #1
(1.) Use the protractor in the applet below to draw a triangle where one angle measures 20° and another angle measures 45°.
(2.) Use the protractor in the applet below to draw a triangle where one angle measures 120° and another angle measures 50°.
Challenge #2
Use the protractor in the applet below to draw a triangle where one angle measures 90° and another angle measures 100°.
Which of the above three triangles is impossible to draw?
Challenge #3
In the diagram below, 9 toothpicks are used to make three equilateral triangles. Figure out a way to move only 3 of the toothpicks so that the diagram has exactly 5 equilateral triangles.
Quiz Time