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C = d or 2 r C = r 2 Area of a Circle Circumference of a Circle A E AB is a diameter AD, DB, and DC are radii EF is a cord B D C F center diameter circle D circumference radius chord • A circle is a plane figure formed by a set of points that are equal distance from a fixed point within it, called the center. • The diameter of a circle is the distance across the inside of a circle through the center. It is twice the measure of a radius. • The radius is half the measure of a diameter. It is a line segment with one end point at the center of the circle and the other endpoint on the edge of the circle. • The circumference of a circle is the distance around it. • A chord is a line segment that connects any two points on a circle. • The area of a circle is the space contained within the circumference. • The ratio of the circumference of a circle to the diameter of a circle is approximately equal to 3.14 or . This ratio is called Pi ( ) and is the same for all circles. 22 7 d = 12 in. ; A = ? d = 12 A = r 2 A 3.14 • (6) 2 A 3.14 • 36 A 113.04 in.2 C = 2 r C 2 • 3.14 • 5 C 31.4 ft r = 6 r = r = 5 ft ; C = ? d 2 r = 12 2 12 in. 5 ft C = d C 3.14 • 10 C 31.4 ft d = 10 ft ; C = ? • • • © Copyright NewPath Learning. All Rights Reserved. 93-4610 www.newpathlearning.com Area & Circumference of Circles

\|xiBAHBDy01665mzV C = d or 2 r C = r 2 Area of a Circle Circumference of a Circle A E AB is a diameter AD, DB, and DC are radii EF is a cord B D C F circle D • A circle is a formed by a set of points that are equal distance from a fixed point within it, called the . • The of a circle is the distance across the inside of a circle through the . It is twice the measure of a . • The is half the measure of a . It is a line segment with one end point at the center of the circle and the other endpoint on the edge of the circle. • The of a circle is the distance around it. • A is a line segment that connects any two points on a circle. • The of a circle is the space contained within the circumference. • The ratio of the circumference of a circle to the diameter of a circle is approximately equal to or . This ratio is called and is the same for all circles. d = 12 in. ; A = ? d = 12 A = r 2 A 3.14 • ( 6 ) 2 A 3.14 • 36 A 113.04 in2 C = 2 r C 2 • 3.14 • 5 C 31.4 ft. r = 6 r = r = 5 ft ; C = ? r = 12 in. 5 ft C = d C 3.14 • 10 C 31.4 ft. d = 10 ft ; C = ? • • • Key Vocabulary Terms • area • center • chord • circle • circumference • diameter • pi ( ) • plane figure • radius © Copyright NewPath Learning. All Rights Reserved. 93-4610 www.newpathlearning.com Area & Circumference of Circles