Is this an equivalent formula for P(A or B or C) ?

[opticaltempest]

I was trying to derive a formula to find $$P(A \cup B \cup C)$$.

I came up with the following:

http://img249.imageshack.us/img249/2154/probabilitymp7.jpg [Broken]

Is that correct?

 

[IMDerek]

Yes it's correct

 

[ZioX]

See Principle of Inclusion-Exclusion for the general result.

http://en.wikipedia.org/wiki/Inclusion_exclusion