Atan

Arctan( x) means 'the angle whose tangent is x.'   So arctan is an angle.

 

Ex        arctan( 1 ) is the angle whose tangent is 1   =  45 degrees,  or in radians pi/4. 

             arctan (sqrt3)  is the angle whose tangent is sqrt(3)  = 60 degrees,  or pi/6  radians.

This and this

¥ ® cosh(^3^31 = Unendlich