Algebra/Circle

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As you likely have learned before, a circle is defined as any set of points that is a fixed distance (the radius) from a fixed point (the center). To find a formula for this, suppose that the center is the point (a,b). According to the distance formula, the distance c from the point (a,b) to any other point (x, y) is:

c² = (x − a)² + (y − b)²

By definition, a circle is the set of all points for a given value of c. We call this r and come up with the following equation for a circle:

A circle with center (a, b) and radius r is the set of all points (x, y) such that

[edit] Examples

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