Unit 7, Lesson 9
Drawing Triangles (Part 1)
Grade 7
Preparation
Lesson Narrative
In this lesson, students build on their observations of triangles with shared angle measures and side lengths, by drawing their own triangles with specified measures: a given angle, two given angles, and two given angles and a given side length.
The purpose of the lesson is to help students see the structure of certain triangles—namely that sometimes the given conditions allow only one possible triangle, sometimes more than one, and sometimes none (MP7). Students also gain experience using various tools to draw triangles with given conditions.
Note that, in grade 7, students are not expected to know that the angle measures within a triangle have a sum of 180 degrees, although it is fine for them to use that information if they know it.
- Draw triangles with two given angle measures and one side length, and describe (orally) how many different triangles could be drawn with the given conditions.
- Use drawings to justify (in writing) whether two given angle measures and one side length determine one unique triangle.
Let’s see how many different triangles we can draw with certain measurements.
Required Preparation
For the digital version of the activity, acquire devices that can run the applet.