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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.
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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