Solve for r
r = \frac{9}{\pi - 1} \approx 4.202479862
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\left(2\pi -2\right)r=18
Combine all terms containing r.
\frac{\left(2\pi -2\right)r}{2\pi -2}=\frac{18}{2\pi -2}
Divide both sides by 2\pi -2.
r=\frac{18}{2\pi -2}
Dividing by 2\pi -2 undoes the multiplication by 2\pi -2.
r=\frac{9}{\pi -1}
Divide 18 by 2\pi -2.
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