A. 2√7

B. √7

C. 4√7

D. 8√7

If x^{2}+y^{2}-4x+6y+c=0 represents a circle radius 5 then c=

The equation of the circle cutting orthogonally the circles x^{2}+y^{2}-8x-2y+16=0, x^{2}+y^{2}-4x-4y-1=0 and passing through the point (1, 1) is

If x^{2}+y^{2}+2gx+2fy+9=0 represents a circle with centre (1, -3) then radius=

The number of common tangents to the two circles x^{2}+y^{2}-8x+2y=0 and x^{2}+y^{2}-2x-16y+25=0 is

From any point on the circle x^{2}+y^{2}=a^{2} tangents are drawn to the circle x^{2}+y^{2}=a^{2} sin^{2}θ. The angle between them is