I'm trying to do the following calculation but nothing works for me

The calculation of `tan-1(1)`

the result of the calculator is `45 grados`

but I can not obtain this result in C #.

Code:

```
Math.Tanh(1);// resultado = 0,761594155955765
Math.Atan(1);//resultado = 0,785398163397448
Math.Tan(1);//1,5574077246549
```

I suppose I should perform some operation with one of them, but what operation and what to use to get the result.