how to find the equation of a circle when given the endpoints and the diameter HELP!

Question

anonymous · Answer

Please post you question and I will be glad to help you.

anonymous · Answer

your*

anonymous · Answer

for example determine the equation of a circle : the line segment with endpoints E(3,0) and F(-3,0) is a diameter of the circle

amistre64 · Answer

$$(x-Cx)^2+(y-Cy)^2=r^2$$

amistre64 · Answer

really?  what point do you see that is the center of 3,0 and 
-3,0?

anonymous · Answer

0,0?

amistre64 · Answer

yep, and how long is half of that line?

anonymous · Answer

0,0?

amistre64 · Answer

$$(x-0)^2+(y-0)^2=r^2$$
$$x^2+y^2=r^2$$

so far

amistre64 · Answer

just need to know how far half the diameter is

anonymous · Answer

which is r

amistre64 · Answer

correct; so if the diamter measures from -3 to 3.... how much would half of it measure out to be?

anonymous · Answer

attachment

amistre64 · Answer

0 is the center of the line; that really doesnt MEASURE anything tho.  we want a distance covered

amistre64 · Answer

if you start at -3 and hop along to get to 3; how far do you travel in the process?

anonymous · Answer

6?

amistre64 · Answer

|dw:1317957847006:dw|

amistre64 · Answer

yes, 6 is the diameter then; and half would be our radius

anonymous · Answer

so 3 is the r but how would i do that in formula form ?

amistre64 · Answer

by filling in the spot that says "r" id imagine.

$$x^2+y^2=r^2$$

$$x^2+y^2=3^2$$

$$x^2+y^2=9$$

anonymous · Answer

oh okay Thanks :D

amistre64 · Answer

yep ...