Objective: Solve equations using area circumference, diameter, and radius.

 Circle: the set of all the points in a plane that are the same distance from a fixed point, aka the center.  Radius: the distance from the center to any point on the circle.  Diameter: the distance across the circle through the center.  Circumference: the distance around the circle.  pi (∏): greek letter representing approx or 22/7

 C=Circumferenced=diameterr=radius  C=∏d  C=2∏r

Find the Circumference Of the Circle C= ∏d C=3.14(16) C≈50.2 cm 28 in Find the Circumference Of the Circle C= 2∏r C=2(3.14)(28) C≈175.8 in 16 cm

 d= 45mi  d= 9.7in  r= 14cm  r= 7.6m C= 3.14(45) C ≈ 141.3mi C= 3.14(9.7) C ≈ 30.5in C= 2(3.14)(14) C ≈ 87.9cm C= 2(3.14)(7.6) C ≈ 47.7m

r d Area of a circle - what’s inside the circle Formula : A = πr 2

10 in A = πr 2 A = π(5) 2 A = π(25) A = 3.14(25) A = 78.5 in 2

 d= 40mi  r= 14cm  r= 7.6m r = 20mi A = 3.14(20) 2 A = 3.14(400) A ≈ 1256mi 2 A = 3.14(14) 2 A = 3.14(196) C ≈ 615.4cm 2 A = 3.14(7.6) 2 A = 3.14(57.76) A ≈ 181.4m 2

The area of a circle is square feet. Find the radius. A = πr = πr 2 π π 169 = r 2 13 ft = r

Find the radius of a circle that has an area of 12,070 square feet A = πr = πr 2 π π = r 2 62 ft = r

C = in C = 2πr = 2πr = 6.28r 9 in = r A = πr 2 A = π(9) 2 A = π(81) A = 3.14(81) A = in 2