Find the area of the shaded region in Fig. 12.22, where a circular arc of radius 6 cm has been drawn with vertex O of an equilateral triangle OAB of side 12 cm as centre.

We know that each interior angle of an equilateral triangle is of measure 60°
Area of sector OCDE =
r2
=
*
* 6 * 6
=
cm2
Area of triangle OAB =
* (12)2
= ![]()
= 36
cm2
Area of circle = πr2
=
* 6 * 6
=
cm2
Area of shaded region = Area of ΔOAB + Area of circle - Area of sector OCDE
=
- ![]()
= (36
+
) cm2