Xo Line is dragged vertically till the angle comes to 45° AKA X4 which means the counted arc equals 90° long.
Horizontally the sine pointer will shift from 0° to 90° at most which means the distance gained equals Sin90=1.
While circlely the additional gain will be 0.58578.
Total length AKA 90°arc will be Sin90 gain + additional gain = 1 + 0.58578 = 1.58578 AKA Phew/2.
So the initial length i.e. X axis and Y axis which equals 1+1=2, becames substracted as far as 0.41422.
This is Phew approach to figure out the circle’s arc as well as circumference.
It takes the real numbers from real circle diagram.