Do you know your SAT polygons?
A quick little formula that will make your life a lot easier in case you come across an SAT problem that asks about polygons is the following:
Total degree measures of a polygon: 180(n – 2), where n = # of sides of the polygon
Say, you have to find the total degree measure of an octagon (that’s the shape of a stop sign). But no need to stop here! We can just plug in ‘8’ for n and we get:
180(8 – 2) = 180(6) = 1080
Another helpful formula to know is the degree measure of any one side of a congruent polygon. A congruent polygon has equal sides, and therefore equal angles. All you have to do is to take the original formula and divide by ‘n’. This makes sense because you are taking the total degree measure and finding out the measure for any one side. So that’s why we divide the total degrees by the number of sides:
[180(n – 2)]/n
Returning to n = 8, let’s assume the octagon is congruent. What is the measure of any of its sides?
180(6) = 1080/n = 1080/8 = 160
Now you’ve learned two useful formulas dealing with polygons!
Degree measure of sides in a congruent polygon:
[(n – 2)180]/n
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About Chris Lele
Chris Lele is the GRE and SAT Curriculum Manager (and vocabulary wizard) at Magoosh Online Test Prep. In his time at Magoosh, he has inspired countless students across the globe, turning what is otherwise a daunting experience into an opportunity for learning, growth, and fun. Some of his students have even gone on to get near perfect scores. Chris is also very popular on the internet. His GRE channel on YouTube has over 10 million views. You can read Chris's awesome blog posts on the Magoosh GRE blog and High School blog! You can follow him on Twitter and Facebook!
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