circles (geom)?

Question

how many lines may be drawn tangent to each of the following?
a. both of two concentric circle
b. both of 2 internally tangent circle
c. both of two externally tangent

thank for any help.... :)

Answer 1

i agree with santmann
a) 0
b) 1
c) 3. one intersecting the segment joining the centers and two that do not.

Answer 2

A) two part answer
a1) none, if the circles are of different radii
a2) infinitely many if the circles have the same radii

b) one

c) one

Answer 3

A) For concentric circle we cannot have any common tangent. (Assuming their radii is different)

B) For internally tangent circle we can have one common tangent

C) For externally tangent circles we can have two common tangents

Answer 4

a)none
b)one
c)three