At which point on the $y$-axis is the line $x = 0$ a tangent to the circle $x^2 + y^2 - 2x - 6y + 9 = 0$?

$A$ circle with centre $(a, b)$ passes through the origin. The equation of the tangent to the circle at the origin is

Let the lines $(2-i)z = (2+i)\bar{z}$ and $(2+i)z + (i-2)\bar{z} - 4i = 0$ (where $i^2 = -1$) be normal to a circle $C$. If the line $iz + \bar{z} + 1 + i = 0$ is tangent to this circle $C$,then its radius is

The slope of the tangent to the circle $x^2 + y^2 = a^2$ at the point $(h, k)$ is:

If the line $x = 7$ touches the circle ${x^2} + {y^2} - 4x - 6y - 12 = 0$,then the coordinates of the point of contact are:

The two circles which pass through $(0, a)$ and $(0, -a)$ and touch the line $y = mx + c$ will intersect each other at a right angle,if