GEOMETRYWhat lies behind us and what lies before us are tiny matters compared to what lies within us.
Ralph Waldo Emerson
Today:– 11.1 Instruction– Practice
11.1 Angle Measures in Polygons
Objectives:• Find measure interior angles of
polygons• Find measure exterior angles
of polygons
Vocabulary: interior angles, exterior angles
polygon# of sides
# of triangles
Sum of interior angles
triangle
quadrilateral
pentagon
hexagon
heptagon
octagon
decagon
20-gon
n-gon
polygon# of sides
# of triangles
Sum of interior angles
triangle 3 1 1x180=180
quadrilateral
pentagon
hexagon
heptagon
octagon
decagon
20-gon
n-gon
polygon# of sides
# of triangles
Sum of interior angles
triangle 3 1 1x180=180
quadrilateral 4 2 2x180=360
pentagon
hexagon
heptagon
octagon
decagon
20-gon
n-gon
polygon# of sides
# of triangles
Sum of interior angles
triangle 3 1 1x180=180
quadrilateral 4 2 2x180=360
pentagon 5 3 3x180=540
hexagon 6 4 4x180=720
heptagon 7 5 5x180=900
octagon 8 6 6x180=1080
decagon 10 8 8x180=1440
20-gon 20 18 18x180=3240
n-gon
polygon# of sides
# of triangles
Sum of interior angles
triangle 3 1 1x180=180
quadrilateral 4 2 2x180=360
pentagon 5 3 3x180=540
hexagon 6 4 4x180=720
heptagon 7 5 5x180=900
octagon 8 6 6x180=1080
decagon 10 8 8x180=1440
20-gon 20 18 18x180=3240
n-gon n n - 2 (n-2)x180
Find the sum of the interior angles of a regular nonagon.
1260°
What is the measure of each interior angle?
140°
Find the measure of each interior angle of a regular quadrilateral.90°
Find the measure of each exterior angle of a equilateral triangle.
120°
Find exterior angle of the same regular quadrilateral. 90°
The sum of the measures of the exterior angles of a convex polygon, one angle at each vertex is ___________.360
What is the measure of an exterior angle for regular hexagon?60°
A regular polygon has exterior angles of 18°, how many sides in this polygon.
20
A regular polygon has interior angles of 150°, how many sides in this polygon.
12
x
x
x
3x 2x
x = 67.5º
x + 20
x
x2x
2x
x = 85º
Find y.
60°
y
y2y
2y
11.1 Angle Measures in Polygons
What lies behind us and what lies before us are tiny matters compared to what lies within us.
Ralph Waldo Emerson
Assignment:• p 708 #1-7 odd
and p 712 #1, 2, 12 – 16
