Circle Geometry

[Probability]

I have a circle and some coordinates, technically I create the circle from the coordinates, then I go on to find the centre of the circle. At this point I am asked to show that this circle has a radius of square root of 13

I thought this;

r² = 2² + ( - 1 - 2)² implies 4 + 9 = 13

r = square root 13

Because I am asked to show that the radius is square root of 13 would this be correct method?

Thanks

 

[mmm4444bot]

If your equation for the circle and the substituted (x,y) coordinates are all correct, then, yes, solving for r as you did is one correct way to determine the radius.

You may also confirm the radius by using the Distance Formula with coordinates at the center and one point on the circle.

Cheers ~ Mark :cool:

 

[Probability]

If your equation for the circle and the substituted (x,y) coordinates are all correct, then, yes, solving for r as you did is one correct way to determine the radius.

You may also confirm the radius by using the Distance Formula with coordinates at the center and one point on the circle.

Cheers ~ Mark :cool:

I don't understand my tutor and yes I asked for clarification but he seems to think that I seemed to think the distance between any two points on the circumference of the circle would equal radius and this is not correct. I have no idea where he got that idea from as I never implied that to him.

The equation of a circle; (x - a)² + (y - b)² = r² using the same x and y values as above gives 13, which he marked correct as this was the next question after the one above, but for some reason he thinks I was trying to find the distance between two points when I answered the question, show the radius of the circle is the square root of 13, which I did;

r² = 2² + (- 1 - 2)² implies 4 + 9 = 13, and

r = square root 13.

My tutor wrote;

r² = (2 - 0)² + (-1 -2)²
= 4 + 9
= 13

Am I wrong ?

 

[JeffM]

I don't understand my tutor and yes I asked for clarification but he seems to think that I seemed to think the distance between any two points on the circumference of the circle would equal radius and this is not correct. I have no idea where he got that idea from as I never implied that to him.

The equation of a circle; (x - a)² + (y - b)² = r² using the same x and y values as above gives 13, which he marked correct as this was the next question after the one above, but for some reason he thinks I was trying to find the distance between two points when I answered the question, show the radius of the circle is the square root of 13, which I did;

r² = 2² + (- 1 - 2)² implies 4 + 9 = 13, and

r = square root 13.

My tutor wrote;

r² = (2 - 0)² + (-1 -2)²
= 4 + 9
= 13

Am I wrong ?

Because you have not given the exact statement of the problem, how in the world can we tell whether you got the right answer?

 

[Probability]

Because you have not given the exact statement of the problem, how in the world can we tell whether you got the right answer?

Jeff that is a fair point, so with that in mind I will have to come back to you because the problem is fairly long and will have to be explained in sections so that readers don't become bored of reading and lost in detail.

I will post it shortly in sections.

Thanks