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
carde.
ICBSE 2015
o be the common centre of​

Answer 1

Angle OEC=90(tangent and radius at point of contact are perpendicular)

by Pythagoras theorem

OC^2=OE^2+CE^2

a^2=b^2+CE^2

√(a^2-b^2)=CE

CD=2CE[perpendicular drawn from centre bisect the chord]

CD=2√(a^2-b^2)