3 5 the polygon angle sum theorems l.jpg
This presentation is the property of its rightful owner.
Sponsored Links
1 / 13

3.5 The Polygon Angle-Sum Theorems PowerPoint PPT Presentation


  • 153 Views
  • Uploaded on
  • Presentation posted in: General

3.5 The Polygon Angle-Sum Theorems. Geometry Mr. Barnes . Objectives:. To Classify Polygons To find the sums of the measures of the interior and exterior angles of polygons. Definitions:. SIDE. Polygon —a plane figure that meets the following conditions:

Download Presentation

3.5 The Polygon Angle-Sum Theorems

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


3 5 the polygon angle sum theorems l.jpg

3.5 The Polygon Angle-Sum Theorems

Geometry

Mr. Barnes


Objectives l.jpg

Objectives:

  • To Classify Polygons

  • To find the sums of the measures of the interior and exterior angles of polygons.


Definitions l.jpg

Definitions:

SIDE

  • Polygon—a plane figure that meets the following conditions:

    • It is formed by 3 or more segments called sides, such that no two sides with a common endpoint are collinear.

    • Each side intersects exactly two other sides, one at each endpoint.

  • Vertex – each endpoint of a side. Plural is vertices.

    You can name a polygon by listing its vertices consecutively.

    For instance, PQRST and QPTSR are two correct names for the polygon above.


Example 1 identifying polygons l.jpg

State whether the figure is a polygon.

If it is not, explain why.

Not D- because D has a side that isn’t a segment – it’s an arc.

Not E- because two of the sides intersect only one other side.

Not F- because some of its sides intersect more than two sides.

Example 1: Identifying Polygons

Figures A, B, and C are polygons.


Polygons are named by the number of sides they have memorize l.jpg

Polygons are named by the number of sides they have – MEMORIZE


Polygons are named by the number of sides they have memorize6 l.jpg

Polygons are named by the number of sides they have – MEMORIZE


Convex or concave l.jpg

Convex if no line that contains a side of the polygon contains a point in the interior of the polygon.

Concave or non-convex if a line does contain a side of the polygon containing a point on the interior of the polygon.

Convex or concave?

See how it doesn’t go on the

Inside-- convex

See how this crosses

a point on the inside?

Concave.


Convex or concave8 l.jpg

Identify the polygon and state whether it is convex or concave.

Convex or concave?

CONCAVE

A polygon is EQUILATERAL

If all of its sides are congruent.

A polygon is EQUIANGULAR

if all of its interior angles are congruent.

A polygon is REGULARif it is

equilateral and equiangular.

CONVEX


Ex interior angles of a quadrilateral l.jpg

x°+ 2x° + 70° + 80° = 360°

3x + 150 = 360

3x = 210

x = 70

Sum of the measures of int. s of

A quadrilateral is 360°

Combine like terms

Subtract 150 from each side.

Divide each side by 3.

80°

Ex. : Interior Angles of a Quadrilateral

70°

2x°

Find m Q and mR.

mQ = x° = 70°

mR = 2x°= 140°

►So, mQ = 70° and mR = 140°


Investigation activity l.jpg

Sketch polygons with 4, 5, 6, 7, and 8 sides

Divide Each Polygon into triangles by drawing all diagonals that are possible from one vertex

Multiply the number of triangles by 180 to find the sum of the measures of the angles of each polygon.

Look for a pattern. Describe any that you have found.

Write a rule for the sum of the measures of the angles of an n-gon

Investigation Activity


Polygon angle sum theorem l.jpg

The sum of the measures of the angles of an n-gon is

(n-2)180

Ex: Find the sum of the measures of the angles of a 15-gon

Sum = (n-2)180

= (15-2)180

= (13)180

= 2340

Polygon Angle-Sum Theorem


Example l.jpg

The sum of the interior angles of a polygon is 9180. How many sides does the polygon have?

Sum = (n-2)180

9180 = (n-2)180

51 = n-2

53 = n

The polygon has 53 sides.

Example


Polygon exterior angle sum theorem l.jpg

The sum of the measures of the exterior angles of a polygon, one at each vertex, is 360.

An equilateral polygon has all sides congruent

An equiangular polygon has all angles congruent

A regular polygon is both equilateral and equiangular.

Polygon Exterior Angle-Sum Theorem


  • Login