It's measured in radians

• Function whose domain is between -1 and 1
• Trig inverse
• Trig angle
• Function of math class
• Inverse math function
• 30В°, for 0.5
• 30°, for 0.5
• Trig function
• Inverse function in trigonometry

Wiktionary Word definitions in Wiktionary
n. (context trigonometry English) Any of several single-valued or multivalued functions that are inverses of the sine function. Symbol: arcsin, sin -1