Question

Points (3,6) and (5,-8) are endpoints of the diameter of a circle.

What is the length of the diameter
What is the center of the circle
What is the equation of the circle

Answer 1

do you know the distance formula ? (How to find the distance between 2 points)

Answer 2

D=y2-y1 ?

Answer 3

Here is a video that explains it.
http://www.khanacademy.org/math/algebra/linear-equations-and-inequalitie/v/distance-formula?exid=distance_formula

Answer 4

So once I calculate the distance, then what?

Answer 5

2\[\sqrt{2}\] (4,-1)

Answer 6

Wow you did that fast

Answer 7

What is the center of the circle? half way between the two points. find the change in y (y2-y1), and go half way up. find the change in x (x2-x1) and go half way over.

Answer 8

sdg's answer is wrong

Answer 9

Thanks for actually showing how to do it phi

Answer 10

I got distance is 14.14213562, the center is (2,-1)

Answer 11

how did you get 2 in (2,-1) (the -1 looks ok)

Answer 12

I used the midpoint formula. (x1+x2)/2,(y1+y2)/2

Answer 13

well, redo the x

Answer 14

Oops, 4

Answer 15

(x - h)^2 + (y - k)^2 = r^2. How do I use this formula to create the equation? I know the radius, but what is h and k?

Answer 16

The diameter is sqrt(200) (which gives you your number), but you might want to write it as
sqrt(100*2)= sqrt(100)*sqrt(2)= 10sqrt(2)
(that is an exact value, and sometimes on multiple choice they will use that version)

Answer 17

(h,k) is the center of the circle.

Answer 18

So I would say, (x-4)^2+(y+1)=7.07060678^2?

Answer 19

(x-4)^2+(y+1)^2=7.07060678^2?

Answer 20

ugly r!
use diameter= 10sqrt(2)
r= 5sqrt(2)
r^2= 5*5*sqrt(2)*sqrt(2)= 25*2= 50

Answer 21

or just square your ugly number you want r^2

Answer 22

lol

Answer 23

I see what you mean

Answer 24

but that's the answer

Answer 25

Thank you very much for the help!

Answer 26

you can check if it is correct
(3,6) is on the circle
so
(3-4)^2+(6+1)^2 should = 50
-1*-1 + 7*7= 1+49=50 yes, it works

Answer 27

awesome!

Answer 28

Thanks a ton