Matthew 3:13-17 The Holy Ghost Descending like a Dove.

The scriptures in Matthew 3 13-17, we are taught about John the Baptist and Jesus Christ.  One of the questions we are asked to consider while reading this assignment is what evidence is found in Matthew 3:16-17 that the father, son, and holy ghost are three separate personages in the god head.  In verse 16 we are told that when Christ came up out of the water that the gates of heaven opened and the spirit of god descended down in the form of a dove. In verse 17 we hear the voice of the lord who says he is well pleased in the choice that Jesus has made. If the god head was one then we would not have heard the lords voice or seen the representative of the holy spirit in the form of the a dove.  There would not have been the need.