The 2 Most Important

Excel Functions AND
Formulas

SUMPRODUCT

AND

INDEX/MATCH

Lesson 3: Excel Spreadsheets  Engineering Functions (40)

In annex 3 you have found a description of all 40 Excel functions in the "Engineering" category. 

If you are using a version of Excel earlier than 2007 you need to activate the "Excel Analysis Toolpack" to make some of the functions above available.