, 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,

I confirm my answer : 8(cm)

Step-by-step 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)

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.