In this lesson, students continue their work from the previous lesson on drawing triangles with specified angle and side measures. Whereas in the previous lesson they focused on two angles and a side length, in this lesson they focus on two side lengths and an angle, and on three angles. They continue to gain experience with compass, ruler, and protractor. They continue to notice from their drawings when the conditions determine one triangle, more than one, or none. Students are not expected to know rules about which conditions determine each possibility.
- Draw triangles with two given side lengths and one angle measure or three given angle measures, and describe (orally) how many different triangles could be drawn with the given conditions.
- Use drawings to justify (in writing) whether two given side lengths and one angle measure determine one unique triangle.
Let’s draw some more triangles.
To help students see how they can use a compass to draw different triangles with two of the same side lengths, you might choose to copy the How Many Can You Draw? blackline master for every student. This is optional.
- Given two side lengths and one angle measure, I can draw different triangles with these measurements or show that these measurements determine one unique triangle or no triangle.