# If a circle S ( x, y) = 0 touches at the point (2, 3) of the line x + y = 5 and (1,2) = 0, then radius of such circle.

Jitender Singh IIT Delhi
8 years ago
Ans:
I am assuming (1, 2) of x + y = 3;
Since both lines are parallel & tangent to circle, so circle must be between them.
Diameter of circle is:
$\sqrt{(2-1)^{2}+(3-2)^{2}} = \sqrt{2}$
$\frac{1}{\sqrt{2}}$