How to Use the Inverse Sine Calculator

Enter a value between −1 and 1. The angle whose sine equals that value comes out in degrees or radians, whichever is selected.

θ = sin⁻¹(x),  for −1 ≤ x ≤ 1

"Inverse sine" and "arcsine" refer to the same function under two different names — sin⁻¹ in most textbook and engineering notation, arcsin in most programming languages. By convention it always returns an angle between −90° and 90° (or −π/2 and π/2 radians), the range needed to make it an actual function rather than something that hands back infinitely many valid angles for one input.