ReferenceExcel FormulasSupported FormulasATANOn this pageATAN The ATAN function returns the arctangent (inverse tangent) of a number in radians. Syntax =ATAN(number) Parameters number: The tangent value to get the arctangent of. Examples =ATAN(1) // Returns 0.7854 (π/4 radians or 45 degrees)=ATAN(0) // Returns 0