The first two, I think, would be called the infinitive form of the passive voice. ) In the last example, the is indicates necessity, obligation or intention rather than anything passive. English is great, because there are times when what seems to be the very same series of words can have a very different meaning.
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AnonymousThe ball is to be found in the bag. People are to be reminded that smoking is prohibited. What kind of grammar is is to be and are to be?All three are examples of the verb (sometimes called a semi- or quasi- modal) am/are is to. This is sometimes referred to as BE to, which I find unhelpful; there is no infinitive.