Section 6.3.notebook
November 16, 2011
Section 6­3: Polygons and Angles
Predict the number of triangles and the sum of the angle measures in a polygon with 8 sides.
# of Sides Sketch of Figure
# of Triangles Sum of Angle Measures 3 4 5 6 7 8 interior angle
an angle that lies inside a polygon
Interior Angle Sum of a Polygon
S = (n ­ 2)180
Examples:
Find the sum of the angle measures of each polygon.
1. hexagon
2. octagon
3. 15­gon
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Section 6.3.notebook
November 16, 2011
equilateral
all sides congruent
equiangular
all angles congruent
regular polygon
if the polygon is equilateral
and equiangular
Measure of One Interior Angle in a Regular Polygon
angle measure =
(n ­ 2)180
n
Examples: Find the measure of one interior angle in each regular polygon. Round to the nearest tenth.
4. octagon
5. heptagon
6. 20­gon
7. A trapezoid has angles that measure 3x , 3x , x , and x . What is the measure of x?
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Section 6.3.notebook
November 16, 2011
8. An irregular heptagon has angles that measure x , x , 2x , 2x , 3x , 3x , and 4x . What is the measure of x?
3