I have been struggling to find a method to do this (that I can understand).

I have a bar with a diameter of 65mm.

It has to have a segment with a 10% cross sectional area of the full circle.

This is the data no angles or arc lengths etc.

I need to calculate the segment width or height.

Thanks in advance if any one can point me in the right direction.

I have drawn it in cad and have a rough idea it is approximately 10mm.

This was done by trial and error.

please see my jpeg image sketch for clarity.

Thankyou

Matt