The line $$a x+b y+c=0$$ will be a tangent to the circle $$x^2+y^2=r^2$$, then

If the tangent at point $$P$$ on the circle $$x^2+y^2+6 x+6 y-2=0$$ meets the straight line $$5 x-2 y+6=0$$ at a point $$Q$$ on $$Y$$-axis, the length of $$P Q$$ is

If a circle of constant radius '$$r$$' passes through the origin and meets the coordinate axes at points $$A$$ and $$B$$ respectively, then the locus of the centroid of triangle $$O A B$$, '$$O$$' being the origin, is

The image of the centre of the circle $$x^2+y^2=a^2$$ with respect to the mirror $$x+y=1$$ is