arcsine is just sin -1 (theta) and can be entered in the calculator as such.
This can be particularly useful when you're trying to find an angle on a right triangle, but you've only been given the lengths of the sides. To find any angle in a right triangle, just take , where o is the side opposite and h is the hypotenuse of the right triangle.
7 ft 6 in means 7 1/2, because 6 in is 1/2 of a foot. 7 ft 8 in means 7 2/3 because 8 in is 2/3 of a foot. 23/3 = 7 2/3. 15/2 = 7 1/2.
23/3 * 15/2 = 57 1/2