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# help Watch

1. okay so I was given the points A, B and the centre C

where A=(-5,2) B=(-1,4) and C=(-2,1)

Okay to find the radius why can we not just find the length of the line from the centre to either of these 2 points?

why do we have to use ?

2. sorry was just seeing how chlorine would look in latex form
3. (Original post by upthegunners)
okay so I was given the points A, B and the centre C

where A=(-5,2) B=(-1,4) and C=(-2,1)

Okay to find the radius why can we not just find the length of the line from the centre to either of these 2 points?

why do we have to use ?
I assume A and B lie on the circle whose centre is C. In which case, yes, you should be able to do that to find the radius; there is no need to use the formula you quote, unless all three points lie on the circle (rather than C lying at the centre).
4. yes you can thats what a and b are for. You put the x and y coordinates of one of the points into the equation to get the answer

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Updated: April 18, 2013
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