Be blessed EssentiallyIslam
Before I attempt to answer your question, let me just explain Izzat, that very much like himself, I am a volunter, nobody pays me to sit here and write. I study theology, which might be the reason, why I possess a significant amount of material in my head.
Anyway back to you EssentiallyIslam
The issue has got nothing to do with the Trinity, but solemenly what underlies the doctrines of both Islam and Christianity, the books.
My point is that the Koran nowhere reveals a organised corruption of the Jewish and Christian books.
If you read my post, you will notice that I refer to several passages in the Koran which state that Jews, Christian and Muslims are all to believe in all the books, within the era of Muhammad.
The passages do not refer to the first Injeel or the first Torah, but the Injeel and Torah which was written by the Jewish and Christians in Muhammad´s era. If that being the case, then the Kitab (Bible, which means book) was not corrupted prior to Muhammad, and even further, in that case they were not corrupted at all.
The problem following, is that Jews and Christians are nowhere in their sacred writings told to believe the Koran, thus we do not need to worry about its teaching nor the fact that the previous books do not match with the Koran.
However, the Muslim has a problem at this point, as he needs to believe in the Koran and the previous books (look at my post) to remain a Muslim, and these two don't match.
Thus, and this is my point, if a Muslim believes in the previous Books, he cannot be a Muslim, which is the very reason why Muslims assert that the previous Books are all corrupt (this is a modern assertion not a Koranic claim, and I am happy to debate this is necessary), yet if he does that, he cannot be a Muslim either, since he has defiled his own religion, which makes it a compulsion to believe in all the books as they were read and understood in Muhammad's era.
Thus the issue is not about Trinity or not, however, unless you believe in the previoius doctrines you cannot be a Muslim, yet if you believe them, you cannot be a Muslim either, so what is a Muslim?
This is the very reason EssentiallyIslam and all the rest of you, that I do not consider anyone of you to be Muslims; there are no Muslims, it's a contradiction in itself.