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

If the lines $3x + 4y - 14 = 0$ and $6x + 8y + 7 = 0$ are both tangents to a circle,then its radius is

The equations of the tangents to the circle $5x^2 + 5y^2 = 1$,parallel to the line $3x + 4y = 1$ are

If the line $3x - 4y = \lambda$ touches the circle $x^2 + y^2 - 4x - 8y - 5 = 0$,then $\lambda$ is equal to

If $P(\frac{\pi}{4})$ and $Q(\frac{\pi}{3})$ are two points on the circle $x^2+y^2-2x-2y-1=0$,then the slope of the tangent to this circle which is parallel to the chord $PQ$ is

The length of the tangent from $(6,8)$ to the circle $x^2+y^2=4$ is