Describe "phase" parameter in astropy.modeling.functional_models.Sine1D and astropy.modeling.functional_models.Cosine1D

[janerigby]

What is the problem this feature will solve?

The documentation for astropy.modeling.functional_models.Sine1D should describe the units of the "phase" parameter. Since it does not, its not clear to the user whether that parameter has the same units of the x-axis (which I would call an x-offset, not a phase), or is it phase in the sense of an angular offset (units of degrees or radians).

Describe the desired outcome

Add description of the "phase" parameter to the documentation of Cosine1D and Sine1D, including units

Additional context

No response

[nden]

Looking at the issue and the code that added it, it was meant as an x- offset. I'm labeling this as a good issue for first time contributors.