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Circles

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.

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Circles

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  1. Circles Learn to find the area and circumference of circles.

  2. 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.

  3. Circumference Radius Center The diameter d is twice the radius r. Diameter d= 2r The circumference of a circle is the distance around the circle.

  4. Find the circumference of each circle in terms of . A. Circle with a radius of 4 m 4m C = 2pr = 2p(4) = 8p m B. Circle with a diameter of 3.3 ft C = pd 3.3ft = p(3.3) = 3.3p ft

  5. d 2 = 1.65 Find the area of each circle in terms of p. A. Circle with a radius of 4 in. 4in A = pr2 = p(42) = 16p in2 B. Circle with a diameter of 3.3 m A = pr2 = p(1.652) 3.3m = 2.7225p m2

  6. 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.

  7. Graph the circle with center (–2, 1) that passes through (1, 1). Find the area and circumference, in terms of p. C = pd A = pr2 = p(6) = p(32) = 6p units = 9p units2

  8. A Ferris wheel hasa diameter of 56 feet and makes 15 revolutions per ride. How far would someone travel during a ride? Use for p. 22 7 22 7  (56)  56 1 22 7 Find the circumference. C = pd = p(56)  176 ft The distance is the circumference of the wheel times the number of revolutions, or about 176  15 = 2640 ft.

  9. Lesson Quiz Find the circumference of each circle in terms of p. 11.2p m 1. radius 5.6 m 2. diameter 113 m 113p mm Find the area of each circle in terms of p. 3. radius 3 in. 9p in2 0.25p ft2 4. diameter 1 ft

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