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Circle equations

Circle equations

From the course: Test Prep: GRE

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Circle equations

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- One other kind of equation you might see in the coordinate plane is the equation of a circle. We are used to dealing with circles in geometry. Finding their areas and their circumferences, but you might have to deal with them in the coordinate plane as well so let me give you the blueprint for the equation of a circle. It's going to be x minus h squared plus y minus k squared equals r which stands for the radius squared. If we have an equation of a circle, I'll give you an example. What if we had one that looked like this. x minus two squared plus y minus two squared equals 16. That would tell me the radius of the circle is four, right, because 16, this number is the radius squared, so we would take the square root of it to find the actual radius, so the radius is four. Then, h and k are the coordinates of the center of the circle. It's always in this format x minus h, y minus k, so the coordinates of the center of this circle because the minus signs here are just part of the…

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