Question

why did Cassius cover his face when dying?

Answer 1

Scroll down here and read about Cassius:

http://nfs.sparknotes.com/juliuscaesar/characters.html

Then read (and re-read if necessary) all of Act V in Julius Caesar. Let us know what you learn. (Original Shakespearean English, on the left; modern-day English, on the right.)
http://nfs.sparknotes.com/juliuscaesar/page_200.html