arc length=

chord length=

where

=angle at the centre measured in radians and R= radius of the circle

using your figures, you get:

and

If you divide the 2 equations above:

or, if we change the variable by:

then you get to:

or:

which is exactly your formula: sin(x)/x=c/s where c is length of chord (2.7)

and s is length of arc (3.6)

The equation can be re-written as:

So it all boils down to finding x = solving this equation which can be done by using numerical methods or a graphical method.

Knowing x will allow you find the angle at the centre =2x

and then the radius of the circle R from:

Now, the distance you have been looking for is