Two circles have the following equations (x -1 )^2+(y -7 )^2= 25 and (x +3 )^2+(y +3 )^2= 9 . 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
Jun 24, 2018

"no overlap "~~18.77

Explanation:

"what we have to do here is compare the distance (d)"
"between the centres to the sum/difference of the radii"

• " if difference of radii">d" then one circle inside other"

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

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

(x-1)^2+(y-7)^2=25," centre"=(1,7), r=5

(x+3)^2+(y+3)^2=9," centre "=(-3,-3),r=3

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

•color(white)(x)d=sqrt((x_2-x_1)^2+(y_2-y_1)^2)

"let "(x_1,y_1)=(1,7)" and "(x_2,y_2)=(-3,-3)

d=sqrt((-3-1)^2+(-3-7)^2)

color(white)(d)=sqrt(16+100)=sqrt116~~10.77

"difference of radii "=5-3=2

"sum of radii "=5+3=8

"since sum of radii"< d" then no overlap"

"maximum distance "=d+" sum of radii"

color(white)(xxxxxxxxxxxxxx)=10.77+8=18.77
graph{((x-1)^2+(y-7)^2-25)((x+3)^2+(y+3)^2-9)=0 [-20, 20, -10, 10]}