Circles Objective: SWBAT define a circle and name its parts. SWBAT use formulas to find the circumference and area of a circle.
Vocabulary Circle a 2-dimensional shape made by drawing a curve that is always the same distance from a center Radius the distance from the center to the edge of a circle Diameter a straight line going through the center of a circle Chord a straight line connecting 2 points on a curve Arc part of the circumference (edge) of a circle Tangent a line that touches a curve at one point, without cutting across it
Center the middle point of a circle Sector a “pie slice” part of a circle Segment an area of a circle made by a line and an arc Circumference the distance around the edge of a circle Area the amount of space inside a 2- dimensional object
Formulas: Circumference C = pi × diameter C = d Area of Circle A = pi × radius × radius A = r2 = 3.14
Label the different parts of this circle. (arc, center, chord, circumference, diameter, radius, sector, segment, tangent) Circumference Segment Chord Tangent Center Arc Diameter Radius Sector
Calculate the circumference of each of these circles Calculate the circumference of each of these circles. Give your answers correct to two decimal places. C = d 1. 2. Radius = 5 ft Diameter = 5 + 5 =10 5 ft 3 in C = 3.14 (3) = 9.42 in C = 3.14 (10) = 31.4 ft
Calculate the area of each of these circles Calculate the area of each of these circles. Give your answers correct to two decimal places. A = r2 3. 4. Diameter = 8 ft Radius = 8 ÷ 2 =4 2 in 8 ft A = 3.14 (2)2 = 3.14 (4) A = 12.56 in2 A = 3.14 (4)2 = 3.14 (16) = 50.24 ft2