An analogy I like is that of a of those holographic card. When you turn the card at different angles it shows the different images that are embedded in it as the light hits it from different angles. So you can have 3 different Images/Persons but in the 1 Hologram/God.

The bottom line of scripture on this topic for me is what Jesus said;
John 8:24 I said therefore unto you, that ye shall die in your sins: for if ye believe not that I am he, ye shall die in your sins.