Find the center and radius of a circle that has a diameter with endpoints (-9, -6) and (-1,0). Show work.

a) center (4,3); radius 5
b) center (8,6); radius 10
c) center (-5,-3); radius 5
d) center (-10,-6); radius 10

Question

Find the center and radius of a circle that has a diameter with endpoints (-9, -6) and (-1,0). Show work.

a) center (4,3); radius 5
b) center (8,6); radius 10
c) center (-5,-3); radius 5
d) center (-10,-6); radius 10

anonymous · Answer

Center would be the midpoint between those two points, and the radius would be the distance between them divided by 2

anonymous · Answer

So I do the midpoint formula using the two points to find the center?

hero · Answer

Graph paper would work great for this problem

anonymous · Answer

Yep, use the midpoint formula

anonymous · Answer

What do you get?

anonymous · Answer

(-5,-3)

anonymous · Answer

Yep, what about for the radius?

anonymous · Answer

I know its suppose to be 5, but I didn't get it.

anonymous · Answer

Do you know the distance formula?

anonymous · Answer

Wait, I think I know why..

anonymous · Answer

I still didn't get it. Isn't it d=$$\sqrt{(x2-x1)^{2}+(y2-y1)^{2}}$$

anonymous · Answer

Yeah thats it. Plug in your coordinates $$D=\sqrt{(-1+9)^2+(0+6)^2}$$

anonymous · Answer

youll get d=sqrt{100}
d=10  

but remember thats the diameter, radius is diameter divided by 2.
10/2=5

anonymous · Answer

Oh, I got it now. I just added wrong. Thanks!

anonymous · Answer

You're welcome