Question 970532: Determine the radius of the circle.(-11,6) Is the circumference of the circle and (-5,2) is the center of the circle. Could you please write the standard equations for this.
Answer by MathLover1(20850)   (Show Source):
You can put this solution on YOUR website! 
Determine the radius of the circle.
( , ) Is the circumference of the circle => (,) could be only one point on the circle
if ( , ) is the center of the circle and and (,) one point on the circle, then radius is the distance ( ) between the center and the point
use distance formula to find the radius:
| Solved by pluggable solver: Distance Formula |
The first point is (x1,y1). The second point is (x2,y2)
Since the first point is (-11, 6), we can say (x1, y1) = (-11, 6)
So  , 
Since the second point is (-5, 2), we can also say (x2, y2) = (-5, 2)
So  , 
Put this all together to get: , , , and
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Now use the distance formula to find the distance between the two points (-11, 6) and (-5, 2)
 Plug in , , , and
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Answer:
The distance between the two points (-11, 6) and (-5, 2) is exactly  units
The approximate distance between the two points is about 7.21110255092798 units
So again,
Exact Distance: units
Approximate Distance:  units
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so, in formula for a circle we need radius squared and it is 
then, from the coordinates of the center we know that  and  and your standard formula is:
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