Math.Atan in c#

Question

Hye  I am having a stupid problem.
As It is Illustrated Tan Inverse(1)==45 In C# It Should Return Math.Atan(1 * Math.PI/180) == 45 but it is not Its is returning something 0.01743.......
I know the degree to radians etc. so please help me out as it is simple question? what is problem behind it, i never noticed and trusted C# calculation, but i cost me a big problem.

Vulpes · Answer

I've just tried the following code but it seems to be working OK to me:
using System;
class Test {    static void Main()    {      double degrees = 45;      double radians = degrees * Math.PI / 180;      double tan = Math.Tan(radians);      Console.WriteLine(tan); // 1      double radians2 = Math.Atan(tan);      double degrees2 = radians2 * 180 / Math.PI;      Console.WriteLine(degrees2); // 45      Console.ReadKey();    } }