Presentation on theme: "Circles Learn to find the area and circumference of circles."— Presentation transcript:
Circles Learn to find the area and circumference of circles.
A circle is the set of points in a plane that are a fixed distance from a given point, called the center. A radius connects the center to any point on the circle. A diameter connects two points on the circle and passes through the center.
Radius Center Diameter Circumference The diameter d is twice the radius r. d = 2r The circumference of a circle is the distance around the circle.
A = r 2 = (4 2 ) = 16in 2 A. Circle with a radius of 4 in. Find the area of each circle in terms of B. Circle with a diameter of 3.3 m A = r 2 = (1.65 2 ) = 2.7225 m 2 d2d2 = 1.65 4in 3.3m
Tweedle Dum & Tweedle Dee will help you remember your circle formulas! Tweedle Dum and Tweedle Dee Around the circle is pi times d. And if the area is declared Then its pi r squared.
A = r 2 = (3 2 ) = 9units 2 C = d = (6) = 6units Graph the circle with center (–2, 1) that passes through (1, 1). Find the area and circumference, in terms of
C = d = (56) 176 ft (56) 22 7 22 7 A Ferris wheel has a diameter of 56 feet and makes 15 revolutions per ride. How far would someone travel during a ride? Use for . Find the circumference. 56 1 22 7 The distance is the circumference of the wheel times the number of revolutions, or about 176 15 = 2640 ft.
Lesson Quiz Find the circumference of each circle in terms of 1. radius 5.6 m 2. diameter 113 m 11.2m 113mm Find the area of each circle in terms of . 3. radius 3 in. 4. diameter 1 ft 9in 2 0.25ft 2