How do Trinitarians explain verses where Jesus claims to have a God?

A little consultation with the commentaries of such verses would clarify that such prayers of Jesus were from his human nature, also see his dual nature and hypostatic union. Jesus worshiped as a human, he was truly a human, but did not cease to be divine in the incarnation. This was an intercessory high priestly prayer for the world that they know the only true God.

Benson writes on John 17:3

Joh 17:1-3. These words spake Jesus — Namely, the words recorded in the three preceding chapters; and lifted up his eyes to heaven — Put himself in the posture of prayer. The following has been called Our Lord’s Intercessory Prayer, because it is considered as a pattern of the intercession he is now making in heaven for his people. In it he comprises all he had said from chap. Joh 13:31, and seals, as it were, all he had hitherto done, beholding things past, present, and to come. It contains the easiest words, and the deepest sense, of any chapter in all the Scriptures; yet is there no incoherent rhapsody, but the whole is closely and exactly connected. Father — This simplicity of appellation highly became the only-begotten Son of God; to which a believer then makes the nearest approach, when he is most full of love and humble confidence. The hour is come — The time of my sufferings is come; glorify thy Son — Let me have such succours from thee as will enable me to bear them; let the circumstances of my trial, both in the Jewish and Gentile courts of judicature, be such as will plainly prove my innocence; and let my death be accompanied with such interpositions of thy power as will remove the scandal of the cross, and demonstrate the relation I stand in to thee; particularly let me be raised from the dead, and taken up to heaven; finally, shed down upon my apostles such miraculous gifts as will qualify them for bearing witness to my miracles, my death, my resurrection, and my ascension. Thus glorifying thy Son, he also will glorify thee — By converting to the belief and practice of true religion, many who will celebrate thy praises eternally. As thou hast given him power over all flesh — Thou hast sent thy Son into the world, and given him power over all men, in this respect, that he can bestow eternal life upon as many as thou hast given him, namely, upon all believers. This is a clear proof that Christ designed his sacrifice should avail for all mankind; yea, that all flesh, every man, should partake of everlasting life. For, as the Father had given him power over all, so he gave himself a ransom for all. And this is life eternal — Is the way to, a preparation for, and a pledge and earnest of life eternal; that they might know — Or, to know, by loving, obedient faith, thee; the only true God — The only cause and end of all things; not excluding the Word that was in the beginning with God, and was God, (Joh 1:1,) nor the Holy Ghost, any more than the Father is excluded from being Lord, (1Co 8:6,) but the false gods of the heathen; and Jesus Christ, whom thou hast sent — To be their prophet, priest, and king. The meaning of our Lord here is, either, “1st, I teach that men should know thee, the only true God, and Jesus Christ whom thou hast sent, as the means of obtaining that eternal life which thou hast given me power to bestow: Or, 2d, Now this eternal life is bestowed by me on men, that they may know thee, the only true God, and Jesus Christ whom thou hast sent; importing that the happiness of eternity will consist in the knowledge of God and Christ. It is justly observed by Grotius, that the Father is here styled, the only true God, in exclusion of those deities which the ignorance and folly of the heathens had introduced. For, as in the latter clause our Lord undoubtedly spake of the Jews, when he mentioned it as the means of eternal life, that they should know Jesus Christ; so, it is probable, that in the former he had the Gentiles in his eye, when he represented the knowledge of the true God as the road to felicity. If so, we cannot from this passage infer that Jesus is not truly, or really God. For, had this been the meaning of the words, would the evangelist have begun his gospel with so solemn a declaration of our Lord’s divinity?

And Ellicot writes on John 20:17

But go to my brethren, and say unto them.—Comp. Notes on Matthew 28:10, and on John 15:15. There is a special force in the word “brethren” as spoken by the risen Lord, in that it declares the continuance of His human nature. (See Hebrews 2:11.)

I ascend unto my Father, and your Father.—The present is used of the future, which He regards as immediately at hand. The message to the brethren is an assurance that the going to the Father, of which He had so often spoken to them, was about to be realised. The victory over death has been accomplished. This appearance on earth is an earnest of the return to heaven. “Unto My Father,” He now says, “and your Father.” It is a more emphatic expression than “our Father” would have been. “I ascend unto My Father. Because He is My Father, He is also your Father, and you are My brethren. My victory over death was the victory of man, whose nature has in Me conquered death. My ascension into heaven will be the ascension of human nature, which in Me goes to the Father.”

My God, and your God.—This phrase contains the same fulness of meaning, and adds the special thought of the continuity of the human nature of our Lord, which has already appeared in the word “brethren.”

1 John 5:20 (ESV) And we know that the Son of God has come and has given us understanding, so that we may know him who is true; and we are in him who is true, in his Son Jesus Christ. He is the true God and eternal life.

Jesus was the last Adam. Adam was created in the image of God but being a created entity, obviously did not have the attributes of omniscience, omnipotence and omnipresence. In order to be the appropriate sacrifice Jesus had to be incarnated in the likeness of Adam, with all the same limitations Adam had. If Jesus had an advantage over Adam (maintaining these attributes outside of having to ask of the Father, just like the first Adam had to) Satan would have had ample argument to accuse God of "hedging him in" as he'd done so when God pointed out Job to him. So having agreed to this, in order to fulfill the atonement, Jesus prayed to the Father.

The early church writers explained the verses where Jesus claims to have a God as referring to both in his divinity and his humanity ( Hebrews 1:8-9). It means that Christ has his own Father as God not only in his human nature but also in his divine nature.

The point is that the dual nature of Jesus has its source from God the Father.

In other words, the Son is God ( by nature) because he is the Son of God ( the Father).

The reason why Jesus is truly God is because he is the Father's only begotten Son [ John 1:1, 14].

This is teaching none other than the Son's functional subordination and ontological equality with the Father.

Reference:

http://www.newadvent.org/fathers/330204.htm

When Jesus replied that; he was speaking from his human standpoint.

The true significance of the death and resurrection of Jesus is that he sacrificed his human life on the cross and then took up that human life again. That is the proof that God has the power over life and death.

Unless Jesus could die physically and take up that physical life again, where would our assurance that he can offer us victory over death.

Remember that God told Adam;

Genesis 3:19 KJV In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return.

The Jesus who made that statement was in his resurrection body, and that body just as yours and mine has an eternal purpose, and so Jesus had to ascend to heaven and to his God who is the same as our God.

Remember that All the sins of the World, were placed on Jesus on the Cross. Therefore the body which was resurrected would not be free of sin until those sins were wiped away by God the father. These Scripture may help you to understand.

1st Corinthians 15:51 Behold, I shew you a mystery; We shall not all sleep, but we shall all be changed,

2nd Corinthians 3:18 But we all, with open face beholding as in a glass the glory of the Lord, are changed into the same image from glory to glory, even as by the Spirit of the Lord.

Jesus resurrection body, just as ours will be much different from our Earthly bodies:

1st John 3:2 Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is.

So the resurrected body of Jesus the man is what we can expect our resurrection bodies to be like:

Romans 6:4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.

And since we know that some will not die but meet Jesus in the air when he returns, there must be a great transformation take place between here and there.

Form the outset, we must remember that Yeshua is both God AND man.

From Isaiah 9:6 we see—

For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace.

A child (Yeshua) could not be given; the son (Logos—the Word) could not be born. Yeshua Messiah is both God and man. As God he is equal with God, and as man he is equal with man.
A child could not be given because Yeshua would have entered into the earth illegally. The child, Yeshua, had to be born in order to satisfy the claims of man. Like wise, Christ could not be born because that would give God a beginning. Christ had to be given in order to satisfy the claims of God.

Yeshua became a man in the womb of Mary, but Messiah (Christ), deity existed eternally. Micah 5:2 John 1:1-2 Psalm 93:2 Psalm 90:2

Hypostatic Union

God becoming a man, or the uniting of humanity with deity, is called the Hypostatic Union:

HUPO: Under

STASIS: That which stands

That which stands under—a foundation.

Literally: Tangibility, reality, substance It is imperative that you identify with Yeshua’s humanity, and equally imperative that you believe in his deity.

Yeshua—Humanity

Messiah (Christ)—Deity

Yeshua Messiah—Hypostatic Union—emphasis on his humanity

Messiah Yeshua—Hypostatic Union—emphasis on his deity

Son of David—Hypostatic Union—emphasis on his humanity

The thrust of a verse containing the name of his hypostatic union is determined by the order of these i.e., whether the action goes from God to man or from man to God. Thus—

Yeshua Messiah—Man to God

Messiah Yeshua—God to man

Philippians 4:19 Ephesians 3:14

Yeshua The Mediator

We (men) approach the mediator in the name of his humanity. He approaches the Father in his deity and receives the answer. We receive the answer to our petition from his humanity. We pray in the name of Yeshua, not in the name of Christ, and not in the name of Yahweh.

Yeshua is not 50‰ God and 50‰ man. He is 100‰ God and 100‰ man. He can satisfy all the claims of God because he is God. He can satisfy all the claims of man because he is man. Yeshua Messiah is God in the form of man; as completely God as if he were not man; as completely man as if he were not God.

Isaiah 9:6

He is God.

He is the Father.

He is deity taking on flesh.

Statements

Humanity

• John 19:28
• Luke 9:58

Deity

• John 8:58
• John 10:30

Hypostatic Union

• Matthew 11:28

His deity did not grow up—his humanity grew up. —Luke 2:40

The child (humanity) grew (human spirit) —Luke 2:52

Yeshua increased in wisdom

Obviously Yeshua could not talk in the cradle as a newborn. —Hebrews 10:5-7

Body = Yeshua

Humanity Did The Work Of Salvation

You believe on his deity to be saved, but his humanity did all the work.

Matthew 16:13

1 John 4:15

1 John 5:1, 5, 10

Salvation is substitution, God cannot die, but Yeshua, as a man, could die. Even if God could die it would not do you any good. God cannot pay for what man has done. That is neither equal nor fair.

Yeshua always said that the son of man must suffer, be turned over, die, etcetera. Matthew 17:12, 22-23 Matthew 26:2 Matthew 28:1-5

In light of the foregoing, I submit that Yeshua, as a man, called upon his God, but as Messiah (deity) he called upon his Father. I believe this is mot clearly seen on the cross. As Yeshua hung there on the cross, dying, his cry was, "My God, my God, why hast thou forsaken me." He did not exclaim, "My Father, my Father...).

Leo the Great wrote for the Council of Chalcedon in 451,

It does not belong to the same nature to say, "I and the Father are one," and to say, "The Father is greater than I." For although there is in the Lord Jesus Christ a single person who is of God and of man, the insults shared by both have their source in one thing, and the glory that is shared in another. For it is from us that he gets a humanity which is less than the Father; it is from the Father that he gets a divinity which is equal to the Father.

The doctrine of the hypostatic union refers to the idea that in Christ there was both a divine and a human nature, simultaneously. This is essential for the work of Christ in our salvation, reconciling the human and divine in his own person, submitting to death on the cross. (Compare Paul in the second chapter of Philippians, for example.)

Your first quotation, from John 20, comes from after the resurrection: Christ declares that his Father is our Father. When he says "my God" he acknowledges the supremacy of God, but not as something distinct from himself; he presents himself as the link between God and humanity, through which God is made known to us. "My God" is also "your God". John Calvin's commentary on the passage says that the phrase 'my God' is "peculiar to his human nature, but is applied to his whole person, on account of the unity, because he is both God and Man."

Likewise, the quotation from John 17 does not imply separation between God and Jesus, but again positions Christ as essential to our knowledge or experience of God. It is possible to make too much of grammar, but the Greek word kai ("and" here) typically has a "positive" or "constructive" sense. So "A kai B" feels something like "not only A, but indeed also B". The import of the passage isn't that we know God, and also Jesus separately - as a student might say that they were majoring in Chemistry and minoring in Drama - but that how we come to know God is through knowing Jesus.