Math CentralQuandaries & Queries


Question from tagbo, a student:

find the eqn of circle passing through (-1 1) and (-1 -4)and whose radiusis 5/2

Hi Tagbo.

Think about what this means. It means the center of the circle is 5/2 units away from both of these two points. How far apart are these particular two points? What does that tell you about where the center is? If you know the center point and the radius, do you know how to write the equation of the circle? Here's a hint: (x - h)² + (h - k)² = r²

Hope this helps,
Stephen La Rocque.

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