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December 15th, 2013, 04:00 AM   #1
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parabola

Tangents are drawn from (-4,0) to . Radius of circles that would touch these tangents and corresponding chord of contact, can be equal to
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December 15th, 2013, 10:42 AM   #2
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If tangent is y = m(x + 4), m(x + 4) = 16x has a repeated root (zero discriminant),
so (8m - 16) - 64m^4 = 0, which implies m = 1.

The points of contact are (4, , so the chord of contact has equation x = 4.

Can you now show that the circle's radius can be 8(?2 + 1)?

Quick follow-up question: what integer value, if any, can the radius have?
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