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U6L1 Perimeter & Circumference • 9-1 Determine the perimeter of a composite figure. • 10-1 Solve problems involving circumference. Perimeter • Perimeter- the distance around a polygon • Polygon- a closed plane figure formed by 3 or more line segments that intersect only at their endpoints (vertices) • To find the perimeter P of a polygon, you add the lengths of its sides. Perimeter Practice P=3+7+3+7 P = 20 Perimeter Practice P=1+5+4+2+7 P = 19 Perimeter Formulas • Square • P = 4S • Rectangle • P = 2L + 2W • Triangle • P=a+b+c • Ormie the Pig Circumference • Circumference = the distance around a circle • Radius = a line segment with one endpoint at the center of a circle and the other endpoint on the circle • Diameter = a line segment that passes through the center of a circle and has endpoints on the circle Formula • r = radius • d = diameter A radius is ½ of a diameter A Diameter is 2 radii (plural of radius) What is Pi? Pi = the ratio of circumference of a circle to length of its diameter Circumference Practice • Which formula do we use? • Why? C = dπ C = 4π Circumference Practice • Which formula do we use? • Why? C = 2π r C = 2π3 C = 6π Assignment P. 456 – 457 #7-10, 17-28 • Day 1 – do only Perimeter problems (Wednesday, 2/13) • Day 2- do circumference problems (Thursday 2/14)