Geometry Notes
In this section, you will learn how to identify and name polygons, considering both convex and concave forms. The definition of a polygon as a closed figure formed by connecting line segments at their endpoints will be explored. You will discover the properties of regular polygons and how to calculate their perimeters. By examining examples and non-examples, you’ll gain deeper insights into polygon characteristics, including the identification of vertices and sides, as well as the application of the distance formula to find side lengths on a coordinate plane.
Geometry Notes
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Presentation Transcript
Geometry Notes Section 1-6
What you’ll 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 polygon, list consecutive vertices • A polygon is • a closed figure in a plane • formed by connecting line segments endpoint to endpoint (these line segments only intersect the other line segments at the endpoints) Consecutive sides E • Parts of Polygons • Each line segment is a called a SIDE • Each endpt where sides meet is a VERTEX • Diagonal • Interior • Exterior P N Diagonal Consecutive Vertices Consecutive Angles 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 onediagonal is outside the polygon
DEFN: Regular Polygon • A polygon is regular if . . . • It is convex • It is equilateral Not Equilateral or Equiangular Not!! Not!! Not Equilateral Regular or Not? Regular or Not? YES Regular or Not? • It is equiangular • Equilateral – all sides are the same length • Equiangular – all angles are the same measure
DEFN: Perimeter of a Polygon • Find the perimeter of PENTA. • The perimeter of a polygon is the sum of all sides. Bet you’ve never heard that one before N 6 in 6 in E T 5 in 5 in P A 7 in • 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 lengths of all sides. . . • Find the length (or measure) of each side • You may have to use the distance formula I told you, this formula would be used all year. . .
Example Please say 3, Please say 3 Find the perimeter of PQR if P(-5, 1), Q(-1, 4) and R(-6, -8). Perimeter = sum of all sides How many sides does a triangle have? So we have to find the length of 3 sides. Oh, yes. . . The distance formula—3 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
