I saw a blog recently saying it was impossible to strike a line at exactly 10 degrees with only a compass and straight line, something called sacred Geometry,
I looked at this and though about it for a while and suddenly saw the way to do it, so after a little practice, I here explain how I did it.
First draw a line and with the compass strike a circle, then using the compass with it set to the same radius, strike an arc an on the new circle draw a line from the centre point through this arc and you have 60 deg Now split this by again striking an arc from the 60 deg line and the base line, again draw a line from the centre point through this new mark and you have 30 deg we now have to find 10 deg, this is done by striking a line from one of the 30 deg lines at an angle, now using the compass mark three point along this line, join the last one to the next 30 Deg line on the circle, now draw a line between the two 30 deg line as per my sketch and using a parallel tool or by creating a parallel offset mark the compass circle with the offset to mark each of the 10 Deg, See the photo above, easy.
I checked it out by setting the compass to the 10 deg and marked it round the circle, and it met up, but the first time it was slightly out because I did not use a straight line between the two 30 deg lines using the slightly out compass line instead, so unless its a fluke this is my way of finding 10 deg without a protractor or drawing it in CAD. No doubt if I have it wrong, some one will let me know.
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