In Fig. 12.30, OACB is a quadrant of a circle with centre O and radius 3.5 cm. If OD = 2 cm, find the area of the

(i) Quadrant OACB


(ii) Shaded region.


(i) Since OACB is a quadrant, it will subtend 90° angle at O

Area of quadrant OACB = * r2


= * * (3.5)2


= * * ()2


=


= cm2


(ii) Area of ΔOBD = * OB * OD


= * 3.5 * 2


= * * 2


= cm2


Area of the shaded region = Area of quadrant OACB - Area of ΔOBD


= -


=


= cm2


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