Area related to Circle chapter-12
Area Related to Circle chapter-12 Circumference of a Circle or Perimeter of a Circle The distance around the circle or the length of a circle is called its circumference or perimeter. Circumference (perimeter) of a circle = πd or 2πr, where d is a diameter and r is a radius of the circle and π = 22 7 Area of a circle = πr 2 Area of a semicircle = 1 2 πr 2 Area of quadrant = 1 4 πr 2 Perimeter of a semicircle: Perimeter of a semicircle or protractor = πr + 2r Area of the ring Formulas : Area of the ring or an annulus = πR 2 – πr 2 = π(R 2 – r 2 ) = π (R + r) (R – r) Length of the arc AB = 2 π r θ 360 0 = π r θ 180 0 Area of sector formula: Area of sector OACBO = π r 2 θ 360 0 Area of sector OACBO = 1 2 (r × l). Perimeter of a sector Formula: Perimeter of sector OACBO = Length of arc AB + 2r = π r θ 180 0 + 2r Other important formulae: Distance moved by a wheel in 1 revolution = Circumfe...