The previous post provided VBA code for a number of trigonometric functions, most of which are already available in Excel. Why bother you may say, why not just use the WorksheetFunction object? The numbers below provide the answer:
Time to calculate ATan2() 65,536 x 16 times  
XL2007 
XL2000 

VBA ATn2() 
1.60 
1.21 
Worksheetfunction 
14.20 
3.06 
With Excel 2007 using a UDF in preference to Worksheetfunction gives a speed improvement of almost 10 times. With Excel 2000 the difference is not so dramatic, but still a worthwhile 2.5 times improvement.
Being picky 
But not for spellers: An Excel blog for engineers and scientists, and an >egineering< and science blog for Excel users.
mrt – OK, fixed.
And congratulations on getting the first comment in :)
Hi Doug 
I followed the link here from Daily Dose of Excel, and I’ll be back, for I’m definitely not one of those $$$ guys.
I really like your concept.
…mrt
Pingback: Excel 2007 performance  feedback please « Newton Excel Bach, not (just) an Excel Blog
Pingback: Worksheetfunction vs UDF  2 « Newton Excel Bach, not (just) an Excel Blog
Pingback: Excel VBA Performance in Office 2007  Code For Excel And Outlook Blog
Pingback: Pendiente compatibilidad 2003/2007 mucho mas lento