These formulaes wer given by my teacher b4 starting dis chapter.....
area of circle = πr² sq.units
circumference or perimeter of circle = 2πr units (or) πd units
area of semi circle = πr²/2 sq.units
circumference of semi circle = πr units
perimeter of semi circle = πr+d units
area of sector = Ф/360 x πr² sq.units
length of arc of sector = Ф/360 x 2πr units
hope dis helps....