3 . The following diagram shows a triangle ABC and a sector BDC of a circle with centre B . The points A , B and D are on the same line .
C
A B D
AB � 1.75r , AC � 1.5r , BC � r , r � 0 , ABC ˆ is acute .
( a ) ( i ) Show that
ˆ 29 cos ABC � . 56
( ii ) Hence , write down ˆ ABC .
It is given that the area of the sector BDC is 9.89 .
( b ) Find r .
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