## EXOEXOEXO one year ago if the point (3,-7) is the center of a circle and the point (8,5) is on the circle, what is the circumference of the circle?

1. jdoe0001

|dw:1439943435490:dw| find the radius keeping in mind that $$\bf \textit{circumference}=2\pi r\qquad r=radius$$

2. jdoe0001

so the radius is really the distance between, the center point, and point on the circle thus $$\bf \textit{distance between 2 points}\\ \quad \\ \begin{array}{lllll} &x_1&y_1&x_2&y_2\\ % (a,b) &({\color{red}{ 3}}\quad ,&{\color{blue}{ -7}})\quad % (c,d) &({\color{red}{ 8}}\quad ,&{\color{blue}{ 5}}) \end{array}\qquad % distance value d = \sqrt{({\color{red}{ x_2}}-{\color{red}{ x_1}})^2 + ({\color{blue}{ y_2}}-{\color{blue}{ y_1}})^2}\to radius$$

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