How Can I Explain the Trinity to a Muslim?

Questions about how to explain the Trinity to a Muslim in a way that helps him understand the oneness of God, whether one could say the Trinity is similar to a person who has multiple personalities, and whether God ever demonstrates the virtues of hope and thankfulness. 

• How can I explain the Trinity to a Muslim in a way that helps him understand the oneness of God?
• Could one explain the Trinity by saying it’s similar to a person who has multiple personalities?
• God both encourages and demonstrates most virtues, but does God ever hope, and is he ever thankful?