Hi possible-san,
Romans 10:9 itself does not prove that Jesus is Jehovah.
I must say I disagree. Examine these verses.
Isaiah 45:21-23 (American Standard Version)
21 Declare ye, and bring it forth; yea, let them take counsel together: who hath showed this from ancient time? who hath declared it of old? have not I, Jehovah? and there is no God else besides me, a just God and a Saviour; there is none besides me.
22 Look unto me, and be ye saved, all the ends of the earth; for I am God, and there is none else.
23 By myself have I sworn, the word is gone forth from my mouth in righteousness, and shall not return, that unto me every knee shall bow, every tongue shall swear.
Philippians 2:10 (English Standard Version)
10 so that at the name of Jesus every knee should bow, in heaven and on earth and under the earth
Are we going to bow down to Jesus or Jehovah? There is only one God.
In addition, the view "Jesus is Jehovah" is not related to the Trinity doctrine.
Once again, I humbly but fervently disagree. "Jesus is Jehovah" is two thirds of the Trinity already. Here is the whole Trinity in one verse.
Matthew 28:19 (New International Version)
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
Notice how it says "name" and not "names"? The only conclusion is that each name is synonymous with the other.
All the best,
Stephen