\\S**t, I type my answer then I pressed "post new answer", then all my work gone.
Anyway, denote point (0.62200155,0.78301601) as point B and (0,1) as point A and center point O. connect point A and O,point B and point O.
The length of major arc AB is r*\(\Theta \) where r=1 since it is a unit circle and \(\Theta \) =asin(y/r)=asin(0.78301601)
r*\(\Theta \)=1*asin(0.78301601)=0.89950000524
you can also verify this with acos=(x/r)
See the following link for visualization:
https://www.desmos.com/calculator/wndlgrvelg
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