In accord with 1Cor 11;3 how can there be a triune god?

Simple. There is no triune God.

Jesus Christ called our God and Father his God and Father.

1 Corinthians 11:3 KJV — But I would have you know, that the head of every man is Christ; and the head of the woman is the man; and the head of Christ is God.

Thats not the only passage of scripture. God the Son came forth from God the Father making him "God in the flesh." 

1 Timothy 3:16 KJV — And without controversy great is the mystery of godliness: God was manifest in the flesh, justified in the Spirit, seen of angels, preached unto the Gentiles, believed on in the world, received up into glory.

The Trinity appears here as in many passages...

John 15:26 KJV — But when the Comforter is come, whom I will send unto you from the Father, even the Spirit of truth, which proceedeth from the Father, he shall testify of me:

Comforter = Holy Spirit

John 14:26 KJV — But the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you.