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