I am now watching the PM PrepCast Episode E07.04.02, and I just learned that:
EAC = BAC / CPI = AC + (BAC - EV) / CPI
I was able to prove the above formula. This is really great fun.
Also, it is clearly mentioned that the above fomulas (2 forms) are same and are used if the Original Estimates were worng (there are variances), and the current performance is correct.
Training for Project Management Professional (PMP)®, PMI Agile Certified Practitioner (PMI-ACP)®, and Certified Associate in Project Management (CAPM)®