Q. If $5x - 12y + 10 = 0$ and $12y - 5x + 16 = 0$ are two tangents to a circle, the radius of the circle is
A) 1
B) 2
C) 4
D) 6
Explanation
(a)
Given tangents $5x - 12y + 10 = 0$ and $5x - 12y - 16 = 0$ are parallel
$\therefore Radius = \left| \frac{c_{1} - c_{2}}{2\sqrt{a^{2} + b^{2}}} \right|$
$= \left| \frac{10 - ( - 16)}{2\sqrt{5^{2} + ( - 12)^{2}}} \right| = \left| \frac{26}{2.13} \right| = 1$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.