Is it obligatory to say the takbir when the Imam stands for the third rak'ah if I am preceded by one or two rak'ahs?

The worshiper follows his Imam in everything, because the Prophet, peace and blessings be upon him, said: "Indeed, the Imam was appointed to be followed. So when he says 'Allahu Akbar', then say 'Allahu Akbar'." And saying 'Allahu Akbar' when standing for the bowing is required from the Imam and the worshiper, and this is indicated by the actions of Abu Hurairah and Ibn Mas'ud, may Allah be pleased with them, in their description of the Prophet's prayer, peace and blessings be upon him.