Solving for the Radius of a Circle in a Sector

[Googl]

Hi all,

I have found this formula being used but I am not sure what it means. It is used to find the radius of a circle in a sector. Hope you can help me understand it.

$$sin(π/6) = r/(6-r)$$

r is the radius of the circle itself and 6 is the radius of the sector or the circle of the sector. I may have to post an illustration if you can understand.

Thank you.

 

[mfb]

A sketch would be useful, indeed.
I expect that the sketch shows what the formula means.