Cheat Sheet for Polygons

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knight247: Legendary Member; Posts: 504; Joined: Tue Apr 19, 2011 1:40 pmFollowed by: 11 members; Thanked: 114 times

by knight247 » Tue Aug 30, 2011 4:35 am

Hey,
I'm kinda well versed with the interior and exterior angle formulas for regular polygons i.e.
(1)Sum of interior angles=(n-2)180
(2)Measure of one interior angle=(n-2)180/n

(3)Sum of exterior angles in one direction is 360 and in the other direction is 360
(4)Measure of one exterior angle=360/n

I'm a little confused though about the formulas for irregular polygons
I know that Formula No.1 still applies. Formula 2 does not. I guess I need some clarification on the exterior angles of irregular polygons. Hoping to get some help on that. Detailed explanations would be appreciated. Thanks

Source: Beat The GMAT — Problem Solving | Tue Aug 30, 2011 4:35 am

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16206; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Tue Sep 06, 2011 7:33 am

knight247 wrote:Hey,
I'm kinda well versed with the interior and exterior angle formulas for regular polygons i.e.
(1)Sum of interior angles=(n-2)180
(2)Measure of one interior angle=(n-2)180/n

(3)Sum of exterior angles in one direction is 360 and in the other direction is 360
(4)Measure of one exterior angle=360/n

I'm a little confused though about the formulas for irregular polygons
I know that Formula No.1 still applies. Formula 2 does not. I guess I need some clarification on the exterior angles of irregular polygons. Hoping to get some help on that. Detailed explanations would be appreciated. Thanks

I wouldn't worry about the formulas for exterior angles.

For irregular polygons (where the sides and angles are not all equal) with n sides, the sum of the interior angle is still 180(n-2) degrees.

Since the angles are not equal in an irregular polygon, there is no formula for each interior angle.

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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