# Geometry Notes Geometry Notes Section 1-6 What youll learn. . . How to identify and name polygons Find perimeters of polygons Vocabulary Polygon Concave Convex n-gon Regular polygon perimeter Polygons Examples

Non examples: DEFN: POLYGON To name a a closed figure in a plane polygon, list formed by connecting line segments endpoint consecutive Consecutive to endpoint (these line segments only sides intersect the other line segments vertices at the A polygon is endpoints)

Parts of Polygons Each E linePsegment is a called a SIDE Each endpt where sides meetNis a VERTEX Diagonal Consecutive Diagonal Consecutive Vertices Interior Angles Exterior T A The name of this pentagon is PENTA.

Convex vs. Concave Polygons Convex Polygons: A polygon is convex if no diagonal is outside the polygon Concave Polygons: A polygon is concave if at least one diagonal is outside the polygon Sides

Name Sides Names of Polygons Name 3 Triangle 8 Octagon 4 Quadrilateral 9

Nonagon 5 Pentagon 10 Decagon 6 Hexagon 12 Dodecagon 7 Heptagon

n n-gon DEFN: Regular Polygon A polygon is regular if . . . It is convex It is equilateral Not Equilateral or Not Equilateral Regular or Not? Not!! Regular

or Not? Not!! YES Regular or Not? Equiangular Itis Equilateral all sides are the same length equiangular Equiangular all angles are the same measure DEFN: Perimeter of a Polygon Find

The perimeter the perimeter of a of polygon PENTA. is the sum of all sides. N 6 in E Bet youve never heard that 6 in one before T 5 in P 5 in 7 in

A Perimeter = 5+6+6++5+7=29 inches Perimeter revisited To find perimeter for a polygon in a coordinate plane Remember, perimeter is the sum of the I told you, this lengths of all sides. . . formula would be Find the length (or measure) of each used all year. .. side You

may have to use the distance formula distance = 2 ( x2 x1 ) ( y2 y1 ) 2 Example Find the perimeter of PQR if P(-5, 1), Q(-1, 4) say and Please 3, R(-6, -8). Please say Perimeter = sum of all sides How many sides does a triangle have?

3 So we have to find the length of 3 sides. Oh, yes. . . The distance formula3 times. Find PQ, QR, and PR using the distance formula. Have you learned. . . How to identify and name polygons? Find perimeters of polygons? Assignment: Worksheet 1.6