Circles

Circle - the set of points at a fixed distance from the center

• Radius - distance from the center

  • R = D/2

• Area = πr²

  • r = radius, π = 3.14

• Circumference - “length” of the circle (perimeter)

  • C = 2πr

• Diameter - the distance of a line going across the circle through the center

  • D = 2r

Length arc

• To find the angle of one piece of a circle

  • 𝚹 = Area of Arc x 360°​ / πr²

    • Length of Arc / Circumference = 𝚹 / 360°

• To find the area of one piece of a circle

  • Area of arc = 𝚹​ / 360° x πr²

    • Area of Arc / Area of Circle = 𝚹 / 360°

ex; r = 5, 𝚹 = 90. find the area of the arc

Area of arc = 90​ / 360° x π x 5²

1/4 x π x 25

Area of arc = 25π/4