Why no cotangent function for radians?

[astrojuanlu]

I saw that there is a cotdg function to compute the cotangent of an angle in degrees. Why its counterpart in radians is not present?

[rkern]

There is no cotdg function in numpy, only in scipy.special. The main reason cotdg is in scipy.special but not cot is that the underlying special functions library that we use for the degree versions implements cotdg as well as sindg, cosdg, and tandg because it can implement cotdg with the same code as tandg just with a slightly different range reduction. That kind of range reduction works well with floating point degrees because a full cycle is a nice even 360, but not with 2*pi radians.

https://github.com/scipy/scipy/blob/master/scipy/special/cephes/tandg.c#L142

[BobBaeck]

cotangent = 1/tan