Perimeter or Circumference of the circle=2πr, where r is the radius of the circle. Or Circumference of the circle = πd, where d is the diameter of the circle.
Area of circle = πr2 where r is the radius of the circle.
Area of Semi circle =πr2 /2
Area enclosed by two concentric circles
= π(R2-r2)
π(R+r)(R- r); R>r
where R’ and r are radii of two concentric circles.
The arc length ‘l’ of a sector of angle ‘θ’ in a circle of radius r is given by l= θ/360 ×2πr
l = θ/180 ×πr
If the arc subtends an angle θ, then area of the corresponding sector is θ/360 ×πr2 .
The sector which is less than the semicircular region, is called the minor sector and the sector, which is more than the semicircular region is called the major sector.
Area of segment= Area of sector – Area of corresponding triangle
Area of major segment = Area of circle – Area of minor segment
Angle described by minute hand in 60 minutes = 360°. Angle described by minute
hand in 1 minute = (360/60) = 6°