Question

,

20. In the figure, O is the centre of the concentric circles of radii 17 cm
and 10 cm respectively. Chord AD of the larger circle cuts the smaller
circle at B and C such that AB = 9 cm. Find
(a) the distance of AD from the centre,

Answer 1

I confirm my answer : 8(cm)

Explanation:

In the triangle OAB, BO²=AB²+AO²-2*AB*AO*cos( BAC)

cos (BAC)=9²+17²-10²/(2*9*17)=15/17

AC/AO=cos(BAC) ==> AC=17*15/17=15

OC²=AO²-AC²=17²-15²=64

OC=8 (cm)