The circle `S_1` with centre `C_1 (a_1, b_1)` and radius `r_1` touches externally the circle `S_2` with centre `C_2 (a_2, b_2)` and radius `r_2` If the tangent at their common point passes through the origin, then

Circle with centre (-1,2) and passing through origin is

Circle with centre (-1,2) and passing through origin is

A circle has its centre on the y-axis and passes through the origin, touches anotgher circle with centre (2,2) and radius 2, then the radius of the circle is

C_1 is a circle with centre at the origin and radius equal to 'r' and C_2 is a circle with centre at (3r, 0) and radius equal to 2r. The number of common tangents that can be drawn to the two circle are :

As shown in the figure,circles with centres A.B and C are externally tangent to each other and internally tangent to the circle with centre D circles B and C are congruent.Circle A has radius 1 and passes through D.The radius of the circle B, is

Let C be the circle with centre at (1, 1) and radius = 1. If T is the circle centred at (0, y), passing through origin and touching the circle C externally, then the radius of T is equal to :

Let C be the circle with centre at (1, 1) and radius = 1. If T is the circle centred at (0, y), passing through origin and touching the circle C externally, then the radius of T is equal to