Thread: first post

Hi, my name is Mike. I'm a student of Cal State Fullerton. I have this problem with L'hospital rule:

the Problem: find values of a and b that satisfy the following

lim (sin x/x^3 + a + b/x^2) = 0
x->0

I tried to combined the whole equation into one using common denominator but it's doesn't seem right at all because I have 2 unknown variables.

Hello and welcome, Mike!

I recommend in the future posting your problems in the appropriate forums, as they will receive more and prompt attention that way.

I think your first move is a good one, i.e., to write:



We have the indeterminate form 0/0, so application of L'Hôpital's rule gives:



In order for this limit to be bounded, we require the numerator to tend to 0, so we need , and we may write:



We have again the indeterminate form 0/0, so application of L'Hôpital's rule gives:



We have again the indeterminate form 0/0, so application of L'Hôpital's rule gives:



Can you now finish?