The word Trinity is not mentioned, but the trinity is certainly noted.
Matt 28:19 Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit.
As far as the Rapture, Jesus himself said that he will return only once more. I don’t know where theologians got the notion that he will come in secret and take those who are his and then return 7 years later for those who change their minds.
True, and I am a believer in the trinity. The point I was making is that many people dismiss the doctrine of the rapture with something along the lines of "the word 'rapture' is not in the bible". God gives us all a certain amount of light (I believe that light was what Jesus was referring to in the parables involving talents - you may believe differently of course), and I'm sure that when we get to heaven each of us will find out that a lot of our cherished beliefs and rejections were wrong.
For the Lord Himself will descend from heaven with a shout, with the voice of an archangel, and with the trumpet of God. And the dead in Christ will rise first. 17 Then we who are alive and remain shall be caught up together with them in the clouds to meet the Lord in the air. And thus we shall always be with the Lord. 1 Thessalonians 4:16-1
Behold, I tell you a mystery: We shall not all sleep, but we shall all be changed-- 52 in a moment, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, and the dead will be raised incorruptible, and we shall be changed. 1 Corinthians 15:51-52
The fact that mankind, who is at enmity with God, routinely discards and denies Scripture that it doesn't understand or doesn't like doesn't mean that the facts of those particular Scriptures are untrue.
Jesus told us in His Book that He will return for His Church before He judges this evil, unbelieving world. He will then return a second time, after the judgment, to set up His millennial kingdom.
All of this can be found in the Bible.