Bellwork

1
Bellwork

• A quadrilateral with both pairs of opposite sides
  parallel is called a ___________________.
• A parallelogram with four right angles is a
  _______________.
• A parallelogram with four congruent sides is
  called a
• _______________.
• A rectangle with four congruent sides is called a
  ____________.
• A quadrilateral with exactly one pair of parallel
  sides is a ________________.

parallelogram
rectangle
rhombus
square
trapezoid
2
BellworkFrom Practice Test

• Which term describes a quadrilateral with two
  pairs of parallel sides?
• A. hexagon
• B. parallelogram
• C. trapezoid
• D. triangle

3
PolygonsClosed figures formed by 3 or more line
segments that do not cross
Objective You will be able to find the angle
measures of a polygon.
4
Please answer these 9 questions on your own
without using your book.What is the name for a
polygon with

• 3 sides?
• 4 sides?
• 5 sides?
• 6 sides?
• 7 sides?
• 8 sides?
• 9 sides?
• 10 sides?
• 12 sides?

?Triangle ?Quadrilateral ? Pentagon ?
Hexagon ? Heptagon ? Octagon ? Nonagon ?
Decagon ? Dodecagon
5
Concave Hexagon
Convex Hexagon

• Polygons can be categorized by their shape.
• A polygon is Convex if any two points inside the
  figure can be connected by a line segment that
  doesnt go outside the figure. We will mostly
  deal with convex polygons.
• A polygon is Concave if any two points inside the
  figure can be connected by a line segment that
  goes outside the figure.

6
Polygon Angle Sum

• For a polygon with n sides, the sum of the
  measures of interior angles is (n-2)180.
• Example a triangle (n3) (3-2)180180
• Find the sum of the angles of
• A decagon. A quadrilateral.

                   
7
Polygon Angle Sum

• Given the pentagon below, what is the value of x?
• n 5, so (n-2)180 540
• 540-100-110-120-115 x
• x _______

115
x
120
110
100
95
8
Types of Polygons

• There are 2 types, regular and irregular.
• Regular polygonsall sides and angles are
  congruent (same length or measure)
• Irregular polygonshave sides and angles that are
  not all the same

Regular Hexagon
Irregular Hexagons
What is the name for a regular quadrilateral? A
regular triangle?
9
Angle Measures of a Regular Polygon

• Remember that the sum of the angles of a polygon
  with n sides is (n-2)180.
• Also remember that all angles are equal in a
  regular polygon.
• We can take the sum of the polygons angles and
  divide it by n (the number of angles).
• Example Pentagon
• (5-2)180 540
• 540 5 108
• So each angle of a regular pentagon is 108.

10
Angle Measures of a Regular Polygon

• What is the measure of each angle in a regular
  octagon?

n 8 (8-2)180 1080 1080 8 135 Each
angle is 135.
STOP
11

• Take a look at 23 on page 439.
• Assignment
• pp. 438-439 1-17 all, 19, 22
• E.C. 28, 32-36 evens