1. Fill in the number of sides Polygon NameNumber of Sides Triangle Heptagon Nonagon Hexagon Pentagon Dodecagon Quadrilateral Decagon Octagon 3 7 9 6 5 12 4 10 8 Find the sum of the measures of the interior angles of a Nonagon. (9 – 2)180 = 7(180) = 1,260 0 03/12/08

2. Ch. 7-6 Areas of Polygons Area is the number of square units the figure encloses. It is flat – 2 dimensional – cm 2 Example: If you were ordering carpet for a rectangular room, you would need to know the area of the room. Important Formulas for finding area: Parallelogram: A = bh where b is the base and h is the height Triangle: A = 1/2bh where b is the base and h is the height Trapezoid: A = 1/2h(b 1 + b 2 )

3. Example 1: Find the area of each figures below. Use the appropriate formula. 3 cm. 7 cm. 6 cm. Area of a Triangle = ½ bh The base is 7 and the height is 3. A = ½ (7)(3) = 10.5 cm. 2 12 cm. 20 cm. 22 cm. Area of a Parallelogram = bh The base is 12 and the height is 20. A = (12)(20) = 240 cm. 2

4. Example 2: Find the area of each figure below. Use the appropriate formula. 3 m. 4 m. 6 m. Area of a Trapezoid = ½h(b 1 + b 2 ) The bases are 6 and 3 and the height is 4. A = ½ (4)(3 + 6) = 18 m. 2 Example 3: Use the area formulas to solve for each unknown below. a.) The area of a parallelogram is 221 yd. 2 Its height is 13 yd. What is the length of its corresponding base? Use the Area formula for a parallelogram, plug in what you know and solve for the unknown. 221 = 13bDivide both sides by 13 b = 17 yd.

5. b.) A triangle has area 85 cm.2 Its base is 5 cm. What is its height? Use the Area formula for a triangle, plug in what you know and solve for the unknown. 85 = ½(5)hMultiply 5 * 1/2 85 = 5/2hDivide by 5/2, since it is a fraction you are really multiplying by the reciprocal! 2/5 * 85 = 5/2h x 2/5 34 cm. = h

6. Ch. 7-7 Circumference and Area of a Circle Important formulas when dealing with circles: Circumference = diameter multiplied by pi or 3.14 C = Circumference = 2 multiplied by the radius multiplied by pi or 3.14 C = Area of a Circle = pi multiplied by the radius squared A = Parts of a Circle: Diameter Radius Chord Circumference

7. Example 1: Find the circumference and area of each object below. Use the formulas given. 45 cm. Find the circumference and area of the basketball hoop C = 45 * 3.14 = 141.3 cm. A = 3.14 * (22.5) 2 = 1589.6 cm. 2 Find the circumference and area of the tire C = 12 * 3.14 = 37.68 in. A = 3.14 * (6) 2 = 113.04 in. 2 12 in.

8. Example 2: Find the area of each irregular figure below. You are going to have to use multiple area formulas. 10 in. 7 in. First find the area of the rectangle. A = length multiplied by width Area of the rectangle = 7 * 10 = 70 in. 2 Next find the area of the semi-circle A = Area of Semi-Circle = ½ (3.14)(5) 2 = 39.25 in. 2 Last, add the two areas together: 39.25 + 70 = 109.25 in. 2

9. Example 3: Find the area of each irregular figure below. You are going to have to use multiple area formulas. 19.8 m. 13.2 m. 6.6 m. First find the area of the rectangle. A = length multiplied by width Area of the rectangle = 19.8 * 13.2 = 261.36 m. 2 Next find the area of the semi-circle A = Area of Semi-Circle = ½ (3.14)(6.6) 2 = 68.39 m. 2 Last need to subtract the area of the semi-circle from the area of the rectangle 261.36 – 68.39 = 192.97 m. 2

10. HW – Pg. 331 PG 331 #1-4 all, 6-10 even PG 338 #4-22 even