Circle equation Yep, that’s right. You have to know the equation of a circle in the xy-plane, even though you probably won’t be asked about it. :/ Standard Equation of a Circle (x-h)^{2}+(y-k)^{2}=r^{2} (h, k) is the circle’s center in the xy-plane; r is the circle’s radius. There are a couple things you’ll need to…

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