Math CentralQuandaries & Queries


Question from Kiera, a student:

Find an equation of the circle that satisfies the stated conditions.

Center C(4,-1), tangent to the x-axis

Hi Kiera,

The equation of a circle with radius r and centre (h, k) is (x - h)2 + (y - k)2 = r2.

A tangent to a circle at a point on the circle is perpendicular to the radius at the same point.


What is the perpendicular distance from the centre to the X-axis? What is the radius of the circle?


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