Question

Tangents are drawn from any point on the circle $x^2+y^2=R^2$ to the circle $x^2+y^2=r^2$. If the line joining the points of intersection of these tangents with the first circle also touch the second, then R equals

• A. $\sqrt{2}r$
• B. $2r$
• C. $\frac{2r}{2-\sqrt{3}}$
• D. $\frac{4r}{3-\sqrt{5}}$

Answer 1

The correct option is B $2r$


$\Delta ABC$ is equilateral
Circum radius = 2 (in radius)
R = 2r