Question

In the given figure, the radii of the circles with centres A and B are 3 cm and 4 cm respectively. Find 

i. d(A,B) in figure (a) 

ii. d(A,B) in figure (b)

Answer 1

i. Here, circle with centres A and B touch each other externally at point C. 

∴ d(A, B) = d(A, C) + d(B ,C)

= 3 + 4 

∴ d(A,B) = 7 cm 

[The distance between the centres of circles touching externally is equal to the sum of their radii] 

ii. Here, circle with centres A and 13 touch each other internally at point C. 

∴ d(A, B) = d(A, C) – d(B, C) 

= 4 – 3 

∴ d(A,B) = 1 cm

[ The distance between the centres of circles touching internaly is equal to the difference in their radii]