Lesson 90
California Saxon Math 6
Classifying Triangles (CC.6.G.5)
At the end of Lesson 90 complete the following activity.
In Lesson 90 we learned how to classify a triangle using information about the angles and/or sides. In this activity, you
will use a ruler, protractor, and compass to draw triangles given three side lengths.
Draw a triangle whose sides have the following lengths: 2, 3 , and 4 centimeters.
Step 1: Draw the longest side first.
Use your ruler to draw line segment AB
with a length of 4 centimeters.
Step 2: Use a compass to draw a circle with its
center at point A and a radius of 2 centimeters.
A
B
Step 3: Use a compass to draw a circle with its
center at point B and a radius of 3 centimeters.
Step 4: The circles intersect at two points. The other vertex of the triangle is at either one of the points the circles
intersect. Note: No matter which of the two points you choose, the triangle will have the same measurements,
so there is really only one possible triangle that can be drawn with the given side lengths.
Step 5: Choose one of the intersection points to be point C, and draw line segments AC and BC to complete the triangle.
C
A
B
Activity Master
Name: __________________________________
For use with Lesson 90 Extension Activity
Classifying Triangles.
1. On a separate piece of paper, draw the triangle from the example by starting with a different base length. Do
the line segments make the exact same triangle as the original? Explain.
Yes, the line segments make the same size and shape triangle as the
original.
2. When you are given three side lengths that form a triangle, do you get a unique triangle or more than one
triangle? Explain.
You get a unique triangle. The triangle can only be formed one way with
that particular size and shape or no triangle can be formed at all.
3. On a separate piece of paper, draw a triangle with sides of 1, 1 , and 3 inches. Do these line segments form a
triangle? Explain.
No, these line segments do not connect to form a triangle.
4. Determine if the given side lengths can be used to form one unique triangle, more than one triangle, or no
triangle. Use a separate piece of paper for your drawings.
a. 2 , 2 , and 5 centimeters
No triangle can be formed. See student drawing.
b. 3, 4, and 5 centimeters
One unique triangle can be formed. See student drawing.
c. 4, 4, and 4 inches
One unique triangle can be formed. See student drawing.
d. 2, 2, and 4 inches
No triangle can be formed. See student drawing.