Hello, fellas. In this session we will learn how to use be + to infinitive.
Be + to infinitive is used to express formal or official arrangements or to give formal instructions or orders.
1) The Prime Minister is to visit Indonesia next month. (formal or official arrangements)
2) All students are to attend the class. (formal instructions or orders)
The structure is often used in newspaper, radio and television reports to talk about future events and expresses near certainty.
1) The government is to increase tobacco duty.
2) A man is to appear in court this morning charged with the murder of the footballer.
Be + to infinitive is commonly used in conditional sentences to express a precondition.
1) They will have to study hard if they are to pass the exam.
2) If I am to catch the train, I shall have to go now.
BBC Learning English, https://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv103.shtml
English Practice, Be + infinitive, https://www.englishpractice.com/improve/infinitive/
Grammaring, BE + TO-infinitive, https://www.grammaring.com/be-to-infinitive