Solve for r
r = \frac{10}{2 \pi - 1} \approx 1.892797511
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2\pi r-r=10
Subtract r from both sides.
\left(2\pi -1\right)r=10
Combine all terms containing r.
\frac{\left(2\pi -1\right)r}{2\pi -1}=\frac{10}{2\pi -1}
Divide both sides by 2\pi -1.
r=\frac{10}{2\pi -1}
Dividing by 2\pi -1 undoes the multiplication by 2\pi -1.
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