This page presents you with a lot of material on the Trinity. As a suitable starting point for Muslim (and non-Muslim) readers our recommendation is to read first at least one of the following five, and then to proceed further in your explorations.
Is it a late corruption? These pages present Trinitarian Quotes from the Early Church (long before the Council of Nicea): , ,  and ... Is The Creedal Doctrine Of The Trinity Biblical?
The Trinity is a fantastic site
on the evidence from the Bible and the early church and very comprehensive.
Uniplurality in the Hebrew Scriptures
Let Us Make Man: A Trinitarian Interpretation of Genesis 1:26 by Anthony Rogers
Our Trinitarian Faith
The Trinity is one of the THE major stumbling blocks in the dialog with Muslims. The following series is my own attempt to relate this part of my faith to you.
What do we really find in the Qur'an about the Trinity?
More, very explicit claims of Jesus to be Deity which are not discussed above
The Biblical data on the Trinity (condensed version)
and a more detailed look at the Old Testament evidence.
A good exposition on The Trinity (Triunity) of God at the Biblical Studies Foundation site.
Trinity from a Jewish perspective: ,  
TAWHID: Belief in one God is a paper discussing both the Muslim and the Christian point of view.
On the philosophical necessity of the Trinity based on the attributes of God
A trilogy of "matheological meditations" on the Trinity,
i.e. mathematical models of "trinity"
([Part One], [Part Two], [Part Three])
If you think that Christian Faith is contradicting reason and logic, you might want to have a look at these books.
And more material on the Trinity by written by other people:
Another web site on the
deity of Christ and the Council of Nicea.
More "hints" on the trinity throughout the Old Testament. A Brief Definition of the Trinity
Response to the "Oneness" Pentecostals a "Christian" church rejecting the Trinity, but before you rejoice, viewing Jesus and God as identical. Nevertheless this trinitarian answer to their claims might help you to understand some of the issues.
Was the Trinity a Christian doctrine before Nicea? - A book recommendation,
A classic in the defense of the Trinity is John Owen's
"Brief Declaration and Vindication of the Doctrine of the Trinity"
[for real heavyweights].
Catholic Encyclopedia: THE BLESSED TRINITY
Who is Jesus?
Who is God?
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