Oy. The word trinity isnt used in the Bible. That is apart of Tradition. The Trinity has always been believed, what it was saying is, their wasnt a DEFINED Doctrine on it until the Councils of the 4th century. Just like with the Eucharistic Sacrament, we know that it was believed to be the Real presence from the beginning, but such confusion and certain types of opposition happened that it was needed to be defined clearly, this doesnt change the fact that the Real presence was there before.
Non-Catholics are constrained to the Bible alone, they chose that path, Catholics and Orthodox are not. Therefore if the Bible never used the word trinity, but Apostolic tradition did, then its still valid. Its much like you. The Quran and the Hadeeth.
Here are some quotations:
The Didache
"After the foregoing instructions, baptize in the name of the Father, and of the Son, and of the Holy Spirit, in living [running] water. . . . If you have neither, pour water three times on the head, in the name of the Father, and of the Son, and of the Holy Spirit" (Didache 7:1 [A.D. 70]).
Ignatius of Antioch
"[T]o the Church at Ephesus in Asia . . . chosen through true suffering by the will of the Father in Jesus Christ our God" (Letter to the Ephesians 1 [A.D. 110]).
"For our God, Jesus Christ, was conceived by Mary in accord with God’s plan: of the seed of David, it is true, but also of the Holy Spirit" (ibid., 18:2).
Justin Martyr
"We will prove that we worship him reasonably; for we have learned that he is the Son of the true God himself, that he holds a second place, and the Spirit of prophecy a third. For this they accuse us of madness, saying that we attribute to a crucified man a place second to the unchangeable and eternal God, the Creator of all things; but they are ignorant of the mystery which lies therein" (First Apology 13:5–6 [A.D. 151]).
Theophilus of Antioch
"It is the attribute of God, of the most high and almighty and of the living God, not only to be everywhere, but also to see and hear all; for he can in no way be contained in a place. . . . The three days before the luminaries were created are types of the Trinity: God, his Word, and his Wisdom" (To Autolycus 2:15 [A.D. 181]).
Irenaeus
"For the Church, although dispersed throughout the whole world even to the ends of the earth, has received from the apostles and from their disciples the faith in one God, the Father Almighty . . . and in one Jesus Christ, the Son of God, who became flesh for our salvation; and in the Holy Spirit" (Against Heresies 1:10:1 [A.D. 189]).
Tertullian
"We do indeed believe that there is only one God, but we believe that under this dispensation, or, as we say, oikonomia, there is also a Son of this one only God, his Word, who proceeded from him and through whom all things were made and without whom nothing was made. . . . We believe he was sent down by the Father, in accord with his own promise, the Holy Spirit, the Paraclete, the sanctifier of the faith of those who believe in the Father and the Son, and in the Holy Spirit. . . . This rule of faith has been present since the beginning of the gospel, before even the earlier heretics" (Against Praxeas 2 [A.D. 216]).
"And at the same time the mystery of the oikonomia is safeguarded, for the unity is distributed in a Trinity. Placed in order, the three are the Father, Son, and Spirit. They are three, however, not in condition, but in degree; not in being, but in form; not in power, but in kind; of one being, however, and one condition and one power, because he is one God of whom degrees and forms and kinds are taken into account in the name of the Father, and of the Son, and of the Holy Spirit" (ibid.).
"Keep always in mind the rule of faith which I profess and by which I bear witness that the Father and the Son and the Spirit are inseparable from each other, and then you will understand what is meant by it. Observe now that I say the Father is other [distinct], the Son is other, and the Spirit is other. This statement is wrongly understood by every uneducated or perversely disposed individual, as if it meant diversity and implied by that diversity a separation of Father, Son, and Holy Spirit" (ibid., 9).
"Thus the connection of the Father in the Son, and of the Son in the Paraclete, produces three coherent persons, who are yet distinct one from another. These three are, one essence, not one person, as it is said, ‘I and my Father are one’ [John 10:30], in respect of unity of being not singularity of number" (ibid., 25).
[216AD]
More here:
http://www.catholic.com/library/Trinity.asp