The throwing sector for all levels of competition has now been standardized to 34.92 degrees for the shot put, discus, and hammer throws. The easiest way to lay out the sector is to get a 90 meter tape measure and have at least 3 people to help.
A 34.92 degree sector is an isoceles triangle in which the unequal side is 0.6 times the length of the other two sides. It can be expressed mathematically as 2arcsin(0.30). The easiest way to lay this out is to remember the ratio 5:3, in which the triangle is 3 meters across for every 5 meters you go out.
Person A should hold the 0 point of the tape measure and the 13 meter mark, on the center of the throwing circle. Person B holds the 5 meter mark, and Person C holds the 8 meter mark. Stretch the tape measure until there is no slack between point each point and place a mark down at each point.
Repeat this procedure again now using points 0 and 26 meters in the center of the circle, 10 meters for person B and 16 meters for person C, marking the points once again.
You can continue marking points using the ratio of 5 meters out 3 meters across, until you have enough points that you feel comfortable to pull a straight line the length of the sector to mark with paint, chalk, or tape.