If the angle of intersection at a point where the two circles with radii 5 cm and 12 cm intersect is 90^o, then the length (in cm) of their common chord is :

The locus of the centres of the circles, which touch the circle, x² + y² = 1 externally, also touch the y-axis and lie in the first quadrant, is :

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 :

If the circles x² + y² + 5Kx + 2y + K = 0 and 2(x² + y²) + 2Kx + 3y –1 = 0, (K$$ \in $$R), intersect at the points P and Q, then the line 4x + 5y – K = 0 passes through P and Q, for :