The trigonometric functions provided in Excel omit some functions, and the functions provided in VBA are still more restricted. Notably VBA does not provide an ATan2 function, which is required to define an angle over a full 360 degree range, based on X, Y coordinates.
The download files below provide the full range of functions, including all inverse functions and hyperbolic functions. The VBA version should work in all versions of Excel from 2000 up, but the Fortran version links to a dll that requires a 32 bit operating system, and does not work in 64 bit versions of Windows.
VBA version: http://interactiveds.com.au/software/TrigFuncsVBA.zip
Fortran version (32 bit only): http://interactiveds.com.au/software/Trig%20Funcs%20dll.zip