Proposal: Trigonometric functions in degrees

Currently PostgreSQL only has trigonometric functions that work in
radians. I think it would be quite useful to have an equivalent set of
functions that worked in degrees. In other environments these are
commonly spelled sind(), cosd(), etc.

Partly, this would be a matter of convenience. It's quite common to
have a problem domain where angles are specified in degrees, and it's
somewhat cumbersome having to type things like sin(radians(x)) and
degrees(asin(x)).

Additionally, functions that worked natively in degrees would be able
to return exact answers in special cases like cosd(90) = 0, whereas
cos(radians(90)) is not exactly 0 because pi/2 cannot be represented
exactly as a floating point number.

Possibly the earthdistance module would benefit from these functions too.

Thoughts?

Regards,
Dean