WHATS THE ANSWER
In Ophelia's description of Hamlet in Act, II, Scene 1, she describes his appearance as disheveled and mad. The reason that Hamlet is putting on such a display is:
Now that his father, the king, is dead he has lost all of his possessions and is no longer going to sit on the throne of Denmark.
He has decided that he absolutely cannot trust Ophelia with the information that he has gained from the ghost.
To learn more about his father's murder and his appearance is part of his "mad act".
To deceive Ophelia into thinking that he is no longer in love with him.
