Question

If a circle S (x, y) = 0 touches at the point (2, 3) of the line

x + y = 5 and S(1, 2) = 0, then radius of such a circle is-

• A. 2 units
• B. 4 units
• C. $\frac{1}{2}$units
• D. $\frac{1}{\sqrt{2}}$units

Answer 1

Answer: (D)

$\frac{1}{\sqrt{2}}$units

Answer 2

Equation of circle (x –2)² + (y –3)² + l(x + y –5) = 0

also (1, 2) lies on it

1 + 1 + l(–2) = 0

Ž l = 1

x² + y² –3x – 5y + 8 = 0

Ž r = $\frac{1}{\sqrt{2}}$units.