# Operator: Arc Cosine

Operator: Arc Cosine

ModPsi
TypeSelector
GroupTrigonometry
Return typeNumber
Parameters
TargetNumber
Technical details
Registry nameoperatorAcos

Operator: Arc Cosine is a Number Spell Piece added by Psi. It will return the arc cosine (or inverse cosine), $\cos^{-1}$ of a number. It is unlocked in the lesson "Trigonometry."

## Parameters

• Target: Requires a number.