The state in which the ma'mum is considered to have caught up with the imam in ruku'

A man entered the mosque while the imam was in ruku', so he said the takbir for ruku'. While he was descending into ruku', the imam was rising from the rak'ah. Did the man catch up with the rak'ah or not? And if he did not catch up with it, when is the rak'ah considered achieved?
Answer: If he reached the position of ruku' before his imam rose, then he has caught up with the rak'ah. If he reached the limit of ruku' before his imam rose, then he has caught up with the ruku'. However, if the imam rose before he reached the limit of ruku', he is considered to have not caught up with it, and he must make up this rak'ah in which he did not catch up with the imam in the state of ruku'. Likewise, if he is in doubt, he must make up this rak'ah; because it has not been established that he caught up with this pillar with his imam. But if he knows that he caught up with the ruku', meaning: he reached the limit of ruku' with his imam, then he counts it, even if his tasbih and tranquility were after that, meaning: even if the tasbih and tranquility were after the imam rose, as long as he reached the limit of ruku' and the imam had not risen.
The presenter: May Allah reward you with good.