http://www.ck12.org Chapter 6. Polygons and Quadrilaterals
Vocabulary
Theinterior angleof a polygon is one of the angles on the inside. Aregular polygonis a polygon that isequilateral
(has all congruent sides) andequiangular(has all congruent angles).
Guided Practice
- Find the measure ofx.
- The interior angles of a pentagon arex◦,x◦, 2 x◦, 2 x◦,and 2x◦. What isx?
- What is the sum of the interior angles in a 100-gon?
Answers:
- From the Polygon Sum Formula we know that a quadrilateral has interior angles that sum to( 4 − 2 )× 180 ◦= 360 ◦.
Write an equation and solve forx.
89 ◦+( 5 x− 8 )◦+( 3 x+ 4 )◦+ 51 ◦= 360 ◦
8 x= 224
x= 28- From the Polygon Sum Formula we know that a pentagon has interior angles that sum to( 5 − 2 )× 180 ◦= 540 ◦.
Write an equation and solve forx.
x◦+x◦+ 2 x◦+ 2 x◦+ 2 x◦= 540 ◦
8 x= 540
x= 67. 5- Use the Polygon Sum Formula.( 100 − 2 )× 180 ◦= 17 , 640 ◦.
Interactive Practice
MEDIA
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URL: http://www.ck12.org/flx/render/embeddedobject/113031