Circles A and B have the following equations (x -4 )^2+(y +3 )^2= 25 and (x +4 )^2+(y -1 )^2= 49 . What is the greatest possible distance between a point on circle A and another point on circle B?

1 Answer
May 21, 2016

d = 20.9443

Explanation:

Circles C_1 and C_2 have respectively centers at
p_1=(4,-3), p_2=(-1,1) and radius r_1=5, r_2=7
Their distance concerning centers is given by
d_{12} = norm (p_1-p_2) = 8.94427.

As we can observe is verified that
r_1 < r_2 + norm (p_1-p_2)
r_2 < r_1 + norm (p_1-p_2)
norm (p_1-p_2) < r_1 + r_2
so the circles intersect in two points.
In this case the maximum distance between C_1 and C_2 is given by
norm (p_1-p_2) +r_1+r_2 = 20.9443