 Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum            Session 4, Part B:
Angles in Polygons

In This Part: Classifying by Measure | Other Classifications | Measuring Angles
Sums of Angles in Polygons

Print several copies of the sample polygons (PDF) and cut out the polygons. These are based on Power Polygons, a set of 15 different plastic polygons, each marked with a letter.

There are numerous ways of classifying angles. One way is according to their measures.  Problem B1 Identify a polygon that has at least one of the following angles:

 a. Acute angle (an angle between 0 and 90 degrees) b. Right angle (an angle equal to 90 degrees) c. Obtuse angle (an angle between 90 and 180 degrees) Problem B2 a. Without using a protractor, find two obtuse angles. Are they in the same polygon? How did you identify them? What do you notice about the other angles in the polygon(s) that has or have an obtuse angle? b. Find a polygon with two or more acute angles. c. Find a polygon with two or more obtuse angles. d. Find a polygon with two or more right angles. e. Can a triangle have two obtuse angles? Why or why not? f. Can a triangle have two right angles? Why or why not?  Try to draw a triangle with two right angles or two obtuse angles. What happens?   Close Tip Try to draw a triangle with two right angles or two obtuse angles. What happens? Problem B3 Which polygons are equilateral triangles (all three sides are equal), isosceles triangles (two sides are equal), or scalene triangles (no sides are equal)? What can you say about the angles in each of these triangles?   Session 4: Index | Notes | Solutions | Video