This is how inverse trigonometric functions are defined in terms of trigonometric functions, where the trigonometric functions are monotonic.
Awen dǎɣ as ashəɣəlan ən maɗinan amləlaynen aqalan atwən dǎɣ ashəɣəlan ən maɗinan, agud was ashəɣəlan ən maɗinan aqalan awaren itəmətuy.