"is to" and "must"

The first one, I suppose.

I would also say the first one.

Though the second one, said with the right intonation, can be used with the meaning 'must', as when a court official says it, it can also be a simple statement of expectation, as when a newspaper announces something that we can expect to see soon.

CJ

But my book says the later!
It says: "The present tense of be plus an infinitive is sometimes used to emphasize duty or obligation.
Compare:
John must appear in c

khoshtipOr I misunderstood!?

Quite possibly. Your book is telling you that the two are nearly equivalent; it's not claiming that either one emphasizes obligation more, but that's what you were asking, and that's what we've told you.

CJ

Yes. At the second read I think the book tells the two are the same. Some odd to me.

khoshtipI think the book tells says the two are the same. Some Sounds odd to me.

It says sometimes 'is to' can mean 'must'—as in the example given in the book.

'sometimes can' isn't the same as 'always does'.

CJ

CalifJimSounds odd to me.

There I meant "It's some odd to me".

khoshtip CalifJimSounds odd to me.There I meant "It's some odd to me".

"It's some odd to me" does not make sense.

According to the definitions of "some" it should not have any issue in that sentence.

khoshtipAccording to the definitions of "some" it should not have any issue in that sentence.

You can't use "some" to modify an adjective. You could say "a bit odd" or "a little odd" or "rather odd" or "somewhat odd".