I don't think that it really matters, whether it is 1, or 10 texts in the Holy Bible, that teaches the Holy Trinity. What is far more important, is the fact that it is a Bible Doctrine.
The Holy Trinity is a term that shows that, while "God" is "One"(Deuteronomy 6:4), there are Three "Persons" in the Holy Bible, Who are equally called "God". No one doubts or questions, that the Father is God. However, when speaking of either Jesus Christ (the Son), and the Holy Spirit, even some who consider themselves "Evangelical", do not fully admit that they are "God" in the same way the Father is. The early Church heresy known as "subordinationism", is quite widespread in many Churches today. Even Bible translations are guilty of this! Because God as "Father" is seen by some to be the "prominent", Person in the "Godhead", as He is said to have "sent" both the Son and Holy Spirit, this has led to a complete misunderstanding of the Holy Trinity. Way back to the time of Origen (A.D.185-254), we have a clearer understanding of the relation of the Persons in the Godhead. Commenting on John 1:1, Origen argued that, the Father is here called "τὸν θεόν" (THE God, "and the Word [Jesus] was with THE God), whereas John calls Jesus "θεὸς", where the Greek article is not used, and therefore understood by Origen to mean, that Jesus was a "lesser god". He also went to the extreme of saying that the "nature" of the Father and Son were not "the same", even though Jesus Himself says that He and "the Father are one" (John 10:30), where the use of the neuter "ἕν" (one), contextually means that they are "one in essence". Sadly, Origen's heresy on Jesus Christ and the Holy Spirit was adopted by some of the "Orthodox" Church at the time, and led to the arch-heretic, Airus in the 4th century, and present day Jehovah's Witnesses.
That Jesus Christ is Almighty God, can be seen in the Old Testament, where in passages like Isaiah 7:14, where He is called "Immanuel", which means, "God-with-us". And in Isaiah 9:6, Jesus is called "’êl Gibbôr" (Mighty God), which is also used for the Father in Isaiah 10:21, where both uses are exactly the same! Paul, informs us in 1 Timothy 3:16, that Jesus Christ is, ""θεὸς ἐφανερώθη ἐν σαρκί" (God manifested in the flesh), which, like 1 John 5:7 (for the clearest verse on the Holy Trinity, where the Greek grammar shows beyond any doubt, has to be the correct reading), has been corrupted to read, "He was manifested", etc, etc! It is important to note, that, the early Church father, Ignatius, who was Bishop of Antioch, and who was born just after our Lord's death, in A.D.35, and was martyred under Trajan (about 108 A.D.). In his epistle to the Ephesians he wrote, "εν σαρκι γενομενοϛ Θεοϛ" (VII.2), which is translated, "God having come in the flesh". This was in Paul's Epistle to Timothy, in the first century! In Romans 9:5, Jesus is called, "God over all"; in Acts 20:28, we read of "God" purchasing the Church by His "blood", clearly a reference to Jesus Christ! In Titus 2:14, Jesus is called "our Great God and Saviour". In Hebrews 1:6, God the Father commands all the angels to "worship" Jesus. And, in verse 8 says to Jesus, "Your throne, O God...". In verses 10-12, again the Father ascribes direct Creation to Jesus Christ, where He applies Psalm 102:25-27, which is used for Almighty God (YHWH), and in Hebrews used for Jesus Christ! In Revelation 1:17, Jesus says of Himself, that He is "the First and the Last" (compare Isaiah 44:6, etc, where it is used for Yahweh). On the phrase itself, " ὁ πρῶτος καὶ ὁ ἔσχατος", Dr Joseph Thayer, who was a Unitarian, and denied the Holy Trinity and Deity of Jesus Christ, said this in his Greek lexicon: "the eternal" (p.253), which can only be used for Yahweh! In Revelation 5:13-14, we read of the whole of creation, ascribing to BOTH the Father AND Jesus Christ, EQUAL "BLESSING, HONOR, GLORY, POWER", and then They are WORSHIPED as God TOGETHER!
Of the Holy Spirit, we see Him as Creator in Job 33:4, and "God" In Acts 5:3-4, where the Greek reads, "τῷ θεῷ" (THE God), and cannot be reduced to anything less! In Hebrews 10:15-18, we read the Holy Spirit using Jeremiah 31:33-34, and applying the words to Himself! Thereby making Himself to be Yahweh! In Ephesians 4:4-6, the Holy Spirit is placed First, and then Jesus Christ, and then the Father, something that would not be possible, if the Spirit were not Himself Almighty God, and equal to both Jesus and the Father!
No honest person who claims to be a Christian, can ever doubt the Great Doctrine of the Holy Trinity. Three Persons, yet One Godhead. Co-equal, Co-eternal, and Co-essential!
AMEN!