If $\theta$ is the angle between the tangents drawn from the point $(-1,-1)$ to the circle $x^2+y^2-4 x-6 y+c=0$ and $\cos \theta=-\frac{7}{25}$, then the radius of the circle is

If the power of the point $(1,6)$ with respect to the circle $x^2+y^2+4 x-6 y-a=0$ is -16 , then $a=$

The radius of the circle passing through the points of intersection of the circles $x^2+y^2+2 x+4 y+1=0$, $x^2+y^2-2 x-4 y-4=0$ and intersecting the circle $x^2+y^2=6$ orthogonally is

A circle passing through the point $(1,0)$ makes an intercept of length 4 units on $X$-axis and an intercept of length $2 \sqrt{11}$ units on $Y$-axis. If the centre of the circle lies in the fourth quadrant, then the radius of the circle is