Sine question

Not sure what you mean but arcsine is just the inverse of sin

$asin[sin\theta]=\theta$

sin (angle)=ratio       (number)

asin (ratio) = angle

sometimes   asin     is  written as   $sin^{-1}$

arc sine  is the same as inverse sine

On a calculator you would normally press Inv or 2nd   and then the sine button if you want inverse sin.