The point on the curve $x^2+y^2=a^2, y \geq 0$,at which the tangent is parallel to the $x$-axis is

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

The diagonals of a rectangle have endpoints at $(0, 0)$ and $(8, 6)$. The equations of the tangents to the circumcircle of the rectangle,which are parallel to these diagonals,are:

If the line $x+y=0$ touches the curve $ax^2 = 2y^2 - b$ at $(1, -1)$,then the values of $a$ and $b$ are respectively:

The straight line $x+2y=1$ cuts the $X$-axis at $A$ and the $Y$-axis at $B$. $A$ circle is drawn through $A, B$ and the origin $O(0,0)$. The sum of the perpendicular distances from $A$ and $B$ to the tangent drawn at the origin to the circle $S$ is:

When is the line $lx + my + n = 0$ a tangent to the circle $x^2 + y^2 = r^2$?