Tuesday, March 31, 2015

Stage Six: Interior and Exterior Angles

The last stage of angles I introduce to my students are interior and exterior angles. This has been the most difficult topic for my students to understand so practicing these formulas is important.

Students need to know that:
- The sum of the measure of the interior angles of a triangle always equals 180 degrees
- The sum of the measure of the interior angles of a quadrilateral is 360 degrees

Interior Angles

To find the sum of the interior angles you use the formula:

180n-360

[EXAMPLE]: The sum of the interior angles of a hexagon is:
 (180 x 6) - 360 = 
ANSWER: 720 degrees

To find out the measure of each interior angle you use the formula:

(180n-360)/n

[EXAMPLE]: The measure of each interior angle of a hexagon is:
(180 x 6) - 360 = 720
720/6 =
ANSWER: 120 degrees

The thing about math is that it is a subject that intertwines often. I have shown this to be true in previous blog posts and will now show it again.

Exterior Angles

The sum of the measure of exterior angles is always 360 degrees

SO, to find the measure of each exterior angle, supplementary and complementary angles need to be understood. First we found that the measure of each interior angle is 120 degrees in the previous examples. Supplementary angles are 180 degrees and complimentary angles are 90 degrees meaning that these interior angles cannot be complimentary but can be supplementary. 

To find the measure of each exterior angle:

We minus 120 from 180 and get 60. Since a hexagon has 6 sides, we would multiply 60 by 6. Is the final result 360? YES! This means our exterior angles are:
ANSWER: 60 degrees

Personally, while I was in school I struggled to understand interior and exterior angles. Be aware of students who are not understanding and provide ways for them to understand outside of the classroom. Here are some useful sources for interior and exterior angles:

WEBSITES:


VIDEOS:







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