| | Re: Polite Requests
Yes - all three are possible. It's nothing to do with grammar but a matter of meaning.
"Can" expresses possibility, so "Can you tell me..." just means "Is it possible for you to tell me..."
in the same way you might use Will - do you remember in mt answer to your previous query i talked about Will expressing volition (willingness to do something) ? So the following would be possible :
A : Sorry, I can't come with you tomorrow - I've got another appointment at that time.
B: Oh never mind. But will you tell me how to get there? I don't know that area.
B is really asking "Are you willing to tell me..."
Now it gets more complicated: Can and will are both first form verbs which have second form equivalents - could and would. Traditionally the second form has been called the "past" tense. But expressing past events is only one of its uses and the label is therefore misleading.
As Lewis points out in his book The English Verb, the function of first form verbs is to express "here and now reality". That's obvious in examples like I live in Milan / I can't ski / It's raining!
Second form verbs on the other hand express "distance from here and now reality". This may be :
a) distance from "now" - ie our traditional "past" : I lived in London as a child / I could ride when I was seven / I didn't go because it was raining
b) distance from reality - ie a hypothetical or imaginary event : I wish I could ski! / Imagine you lived on Mars. What might your life be like? / If you won the lottery, what would you do with the money?
c) Psychological distance. Compare the difference in tone (and therefore psychological effect) between a) Hi John - I want to speak to you for a moment and b) Hi John, I wanted to speak to you for a moment. The use of the second form makes it more polite - because distanced from "here and now reality" and therefore more indirect.
The same is happening with the differences between:
Can you tell me...
Could you tell me ...
Will you tell me...
Would you tell me...
As almost always with verbs, grammar is unimportant. It's the meanings they express which determine which form a speaker chooses to use.
Hope that clarifies.