Circular Logic
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Updated June 3rd, 2015
The Story
    The graph of y = x2 is the u-shaped, blue curve to the right. When a circle is dropped into this parabola, it will be tangent to the graph at two points if its radius is large enough, as the red circle, or at one point otherwise, as the green circle. Find the radius, b, of the largest circle which is tangent to the parabola at only one point.

Submitting Your Solution

    Credit will be awarded on the following guidelines:
  • Writing and solving a system of 2nd degree equations that represent the problem, and
  • Including other details, such as a rationale that explains the value of your radius.

    Click here if you would like to submit your solution via e-mail to