Question

What is the length of RS.

Answer 1

Consider, in ΔRPQ,

RP = R (Radius of larger circle)

PQ = r (radius of smaller circle)

We have to find, RQ, by Pythagoras theorem,

RP² = PQ²+RQ²

R² = r²+RQ²

RQ² = R²-r²

RQ = √(R²-r²

Now, as RQ & QS both are tangents of the smaller circle, their lengths must be equal. so, RS = 2 × RQ

RS = 2√(R²-r²)