Calculating Radius of Circle: X^2 - 2Ax + Y^2 - 2Ay = 0

[m00c0w]

I'm trying to calculate the radius of the circle x^2 - 2ax + y^2 - 2ay = 0
I completed the square and got to (x-a)^2 + (y-a)^2 = 2{a}^2
That would mean the radius is \sqrt{2{a}^2} right? Which would be \sqrt{2}\sqrt{a^2} \Rightarrow a\sqrt{2}... but my textbook quotes the answer as \sqrt{2a} Did I do something wrong or is my textbook incorrect?

 

[arildno]

Your textbook is wrong.

 

[HallsofIvy]

Are you sure you are reading your textbook? It might be that the answer is \sqrt{2}a[/tex] but a little blurred so it is not clear where the square root sign ends- it looks like \sqrt{2a}. <br /> <br /> On the otherhand that is exactly why most texts would use the clearer a\sqrt{2} as you do.