![]()  | 
  
    Stan Math Library
    5.1.0
    
   Automatic Differentiation 
   | 
   
Return the principal value of the arc tangent, in radians, of the first variable divided by the second scalar (cmath).
The derivative with respect to the variable is
\( \frac{d}{d x} \arctan \frac{x}{c} = \frac{c}{x^2 + c^2}\).
| a | Numerator variable. | 
| b | Denominator scalar. |