Circle A has a radius of 4 and a center of (8 ,5 ). Circle B has a radius of 2 and a center of (6 ,1 ). If circle B is translated by <3 ,1 >, does it overlap circle A? If not, what is the minimum distance between points on both circles?

1 Answer
Jul 26, 2017

"circles overlap"

Explanation:

"what we have to do here is compare the distance (d )"
"between the centres of the circles to the"
color(blue)"sum of the radii"

• " if the sum of radii > d then circles overlap"

• " if the sum of the radii < d then no overlap"

Before calculating d we require to find the coordinates of the new centre of B under the given translation which does not change the shape of the circle only its position.

"under a translation "((3),(1))

(6,1)to(6+3,1+1)to(9,2)larrcolor(red)" new centre of B"

"to calculate d use the "color(blue)"distance formula"

color(red)(bar(ul(|color(white)(2/2)color(black)(d=sqrt((x_2-x_1)^2+(y_2-y_1)^2)color(white)(2/2)|)))

(x_1,y_1)=(8,5),(x_2,y_2)=(9,2)

d=sqrt((9-8)^2+(2-5)^2)=sqrt(1+9)=sqrt10~~3.162

"sum of radii "=4+2=6

"since sum of radii > d then circles overlap"
graph{(y^2-10y+x^2-16x+73)(y^2-4y+x^2-18x+81)=0 [-20, 20, -10, 10]}