I am not looking for mathematical formula but some kind of combination how to count arcsine. I found a way, but I feel that it must exist some easier way, some kind of combination which let a user to obtain the result much faster, so this problem is not a question about numerical methods but using built-in application (calculator and application are in the list). I've asked the crew for help but the only answer was :
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So can anybody help with this simple problem?