Question

Out of the two concentric circles, the radius of the outer circle is 5 cm and the chord AC of length 8 cm is a tagnent to the inner circle. Find the radius of the inner circle.

Answer 1

Let say, the centre is O

OA = 5cm,

$\frac{AC}{2}$ = 4cm,
distance of O from AC =$\sqrt{(5^2-4^2)}$

$\Rightarrow \sqrt{9}$ =3
Tangent to the inner circle
so, radius = 3cm