Math problem - Hard?

Question

A circle of unknown radius has a chord of length d whose midpoint is 1 foot from the circle. Find the radius, r, of the circle [in inches].

Answer 1

Here are the 3 formulas you need:

a) D = 2 * R * sin(a/2)
b) 1(foot) = R * cos(a/2)
and the conversion:
c) sin^2(a/2) = 1 - cos^2(a/2)

Square equations a) and b) and make the substitution so it's sin^2(a/2) on both sides, then solve algebraically.

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Answer 2

Yea, thats a pretty hard question, but i think its (1+ squrt of 5) divided by 2