Hi! A question on madness in Hamlet

Hamlet is sane throughout the play. If he were not sane, he could not have stopped being insane when he chooses.

That part I have it down.

BUT at the end of the play, Hamlet pleads madness as an excuse for causing the death of Ophelia, this madness has a different meaning. Hamlet is alluding to his inability for self control, his slavery to passion and revenge. With an outburst of anger, he kills polonius, thinking he were the king.

But are there any other places where I can prove that Hamlet is indeed mad, in his lack of control and habitual unbalance.


Thanks