This construction shows angles AOF=40 degrees, BOE= 90 degrees, BOF= 140 degrees, BOG=70 degrees, BOH=35 degrees and BOI=17.5 degrees. From the simple construction of 40 degree angle using compass, pencil and ruler only, a wider range of other angles such as 5, 10, 20, 25, 35, 50, 70, 130, 140 etc can be derived. Eureka!!!