Why is Aryoch no w called "Shalita Di Malka"?
Malbim: Daniel did not ask him because he is the executioner, rather, because he is one of the king's great officers. This is a reason why he should know.
What is the meaning of "Al Mah Dasa Mehachtzefah"?
Rashi: Why did the king make this radical decree?
What did Aryoch tell Daniel?
Rashi: He was angry that no one told him the dream.
Daniel was in Sha'ar ha'Melech. Did he not already know the decree?
Malbim (14): Daniel knew about the dream, but he did not want to endanger himself to get involved. Once he saw that he stands to be killed, he wanted to tell the king. However, they will ask him why he was silent until now! Therefore, he pretended that until now, he did not know about the dream.
