Required accessories - pencil, compass, unmarked straightedge

Odd proportion angles (there is a proportion of the steam angles) of the3 (which may be 5,7,9, ...) and theelement$\displaystyle 45 ^ o$ (which can be any angle which is obtainable by means of compass and straightedge)base angle

The angle CAB $\displaystyle 45 ^ o$ can be obtained with a compass and unmarked ruler, he added angles (each have $\displaystyle 45 ^ o$) DAC and EAD, obtained angle EAB $\displaystyle 135 ^ o$is thestarting angle

Merge points E (D, C, B) and get a longer ED (DC, CB)

Along the DC from the point C draw is normal that intersects the segment AB, the intersection is a point G

Divider AG and from point G draw a circular arc to a longer EA and H get the point, and the arc GH, join the dots G and H and get along GH

Longer GH (ED, DC, CB) are equal, the arc EB'scan be made smaller or larger with a constant radius AB, arc GH is thefirst circular arccan be made smaller or larger with a constant radius AGsecond circular arc

INCREASING THE ANGLE

the starting angle EAB add angle FAE $\displaystyle 15 ^ o$ get the angle FAB $\displaystyle 150 ^ o$ - continued in the next post