1. An equiangular octagon must have 8 equal exterior angles that sum to 360°; i.e. they must each be 45°
2. Starting from (0, 0) move a distance 1 (the first length in the list) to the right.
3. Turn 45° anticlockwise and move a distance 2 (the 2nd distance in the list) in that direction. This will take you a further distance 2cos(45°) [or 2/sqrt(2)] in the x-direction, and a distance 2 sin(45°) [also 2/sqrt(2)] in the y-direction.
4. Turn another 45° and move the next distance specified in the list.
5. Keep repeating the above until you land back at (0, 0).
The max and min values of x and y can be found by keeping track of the cumulative sum of stepsize*cos(step*45°) for x, and stepsize*sin(step*45°) for y.