JEE Main 2019 Mathematics question
The line x = y touches a circle at the point (1, 1). If the circle also passes through the point (1, −3), then its radius is:
Answer: (C)
Solution
Centre (h, 2 − h) on the normal; equidistant from (1, 1) and (1, −3) ⇒ h = 3, radius .