What is prescribed for one who joins the prayer late if he catches the Imam bowing, and is it a condition for catching the rak'ah that he says: "Subhana Rabbiyal Azeem" (Glory be to my Lord, the Most Great) before the Imam rises?

If a worshiper joins the Imam while he is bowing, that rak'ah counts for him, even if the worshiper does not recite the tasbeeh until after the Imam has risen. This is based on the Prophet's (peace be upon him) saying: "Whoever catches one rak'ah of the prayer has caught the prayer." A rak'ah is caught by catching the bowing. The proof for this is the action of Abu Bakrah Al-Thaqafi when he bowed outside the row and then entered it. The Prophet (peace be upon him) did not order him to repeat the rak'ah, but rather forbade him from repeating the bowing outside the row.