Two circles have the following equations (x -2 )^2+(y -4 )^2= 36 and (x +8 )^2+(y -7 )^2= 49 . Does one circle contain the other? If not, what is the greatest possible distance between a point on one circle and another point on the other?

1 Answer
Apr 19, 2016

One circle does not contain the other rather they intersect each other. The greatest possible distance between a point on one circle and another point on the other is 23.44.

Explanation:

(x-2)^2+(y-4)^2=36 is a circle with center at (2,4) and radius 6.

(x+8)^2+(y-7)^2=49 is a circle with center at (-8,7) and radius 7

The distance between centers of two circles is sqrt((2-(-8))^2+(4-7)^2) or sqrt(10^2+3^2)=sqrt109=10.44

As the distance between centers is 10.44 and radius of two circles is 6 and 7 but distance is less than sum of radii, one circle does not contain the other rather they intersect each other.

The greatest possible distance between a point on one circle and another point on the other is 10.44+7+6=23.44.

graph{((x-2)^2+(y-4)^2-36)((x+8)^2+(y-7)^2-49)=0 [-30, 30, -15, 15]}