Let’s solve some important questions:
Q.1: Three semicircles each of diameter 3 ??, a circle of diameter 4.5 ?? and a semicircle of radius 4.5 ?? are drawn in the given figure. Find the area of the shaded region.

Solution: Let us label the smaller semicircles as ?,? and ?, the circle as ? and largest semicircle as ? respectively. Then,
Radius of semicircle ?=(3+3+3)/2=9/2 ??
Diameter of circle ?= Radius of semicircle ?
⇒ Radius of circle ?=4.5/2=9/4 ??
Area of semicircle ?=1/2?(9/2)2=(81/8)? ??^2
Area of smaller semicircles =1/2?(3/2)2=(9/8)? ??^2
Area of circle ?=?(9/4)2=(81/16)? ??^2
Area of shaded region = Area of semicircle ?+ Area of semicircle ?− (Area of semicircle ?+ Area of semicircle ?+ Area of circle ?)
=(81/8)?+(9/8)?−[(9/8)?+(9/8)?+(81/16?)]=(63/16)?=63/16×22/7=12.375 ??^2
Q.2: A chord ?? of a circle of radius 10 ?? subtends an angle of 60° at the centre of circle. Find the area of major and minor segments of the circle.
Solution:
Join ?? and ??.
In Δ???,
??=?? and ∠???=60°
⇒Δ??? is equilateral.
∴ Area of Δ???=(√3/4)(10)^2=25√3≈43.25 ??2
Area of minor sector ???=(60/360)×(22/7)×(10)^2=(50/3)?=52.38 ??2
⇒ Area of minor segment =52.38−43.25=9.13 ??2
∴ Area of major segment =?(10)^2−9.13=314−9.13≈304.87 ??2