Question

$\ell x+my+n=0$ is a tangent line to the circle $x^2+y^2=r^2$, if -

• A. ${\ell }^2+m^2=n^2{r}^2$
• B. ${\ell }^2+m^2=n^2+r^2$
• C. $n^2=r^2\left({\ell }^2+m^2\right)$
• D. none of these

Answer 1

Answer: (C)

Correct answer is (c) $n^2=r^2\left({\ell }^2+m^2\right)$