Hello, my question concerns the practical implementation of the complex inverse tangent function atan(z) in Scilab.
In the source code of Scilab, the file "watan.f" (in the elementary functions) seems to compute this function as atan(z) = i/2 log((i+z)/(i-z)), where i^2=-1. Yet, when comparing the result given by atan(z) and %i/2*log((%i+z)/(% i-z)) in Scilab, they are different for every point on the imaginary axis excepted in the unit circle. For instance, z = 2*%i disp([atan(z),%i/2*log((%i+z)/(%i-z))]) -> 1.5707963 + 0.5493061i - 1.5707963 + 0.5493061i I would like to know where does the difference comes from and if 'watan.f' is really the file that computes atan. The values obtained with the function atan(z) seem to coincide with another definition of atan(z) : atan(z) = 1/(2i) [log(1+iz)-log(1-iz)] which is used by Mathematica and the function 'catan' in linux. Pierre _______________________________________________ users mailing list [email protected] http://lists.scilab.org/mailman/listinfo/users
