Question

two concentric circles of radii a and b(a>b)are given.find the length of the chord of the larger circle which touches the smaller circle.

Answer 1

Consider the figure attached.
The chord of larger circle which touches the smaller circle should be tangent to it at the meeting point. Therefore the length could be found using Pythagoras theorem.
$chord \: length = 2 \times \sqrt{ {a}^{2} - {b}^{2} }$