Recent content by mad

  1. M

    Integration by trig. substitution

    Woops. Was this the only problem? I think this only changes the arctg from the final answer and not the ln(..) of the answer. I hate when this type of error happens..
  2. M

    Integration by trig. substitution

    Hello everyone I have an exam tomorrow and I would really appreciate if someone could tell me what I did wrong with this exercice. I did it on paper and I scanned it. Here is the link to the scan: The answer in the book is sqrt(x^2 + x +5/4) + 2ln(sqrt(x^2 + 2x + 2) + x +1) + C...
  3. M

    Is my book wrong?

    Thanks for your help, Daniel. I see my solution was okay. We had to do the problem by exponents of sec and tg. (sorry I dont know what the method is called in english) However, what does d(cos u) means in your solution? and I know you replaced a sin^4 (u) by (1-cos^2 (u)), but where is the...
  4. M

    Is my book wrong?

    I have this integration problem that I did but it doesnt give me the right answer. But there are like 3 other similar exercices I did the same way and I got all the right answers.. maybe it is my book (I dont think so ... :p) It's an integration problem: \int tg^3(4x) sec^4(4x)dx heres...
  5. M

    Integration problems

    Hello everyone. I have been trying to do those 2 exercices for a while now and I can't get it.. We just started doing Integration by parts (is that how you call it in english?) here are the problems 1) \int{ (x^3)(e^{x^2})} and 2) \int{ \frac{{(x)(e^x)}} { (x+1)^2}} for the 2nd...
  6. M

    Limit problem

    I knew it was that simple!! Thanks for the help :)
  7. M

    Limit problem

    Hello, I have two questions concerning limits 1) lim x-> 0+ x^(sinx) 2) lim x-> +inf. (9^x)/(8^x) The first one gives me 1 (e^0 = 1) .. is that correct? The 2nd one I dont know how to do. Can someone please explain the 2nd one for me? Thanks a lot
  8. M

    Limit question (inf. - inf.)

    This one. I will try your method. Is it the only way?
  9. M

    Limit question (inf. - inf.)

    I edited the equation. It was a typo.. sorry
  10. M

    Limit question (inf. - inf.)

    That's the answer in the book =) Sorry, it was x - (lnx^2-1)
  11. M

    Limit question (inf. - inf.)

    EDITED THE EQUATION Hello all, I have this problem I can't solve.. it is a infinite - infinite. I tried it around 5 times and can't find the correct answer (infinite). I'm pretty sure I have to put in evidence x^2 and use a limit law but I can't find the answer.. can someone help me for...
  12. M

    Can I do this? (integral)

    If by substitution you mean posing u=.. then replacing it, yes, we saw this in class. I think I'll do what you said, since it seems like the only method (doing them in the scalar form). I tried to do them this way so I didnt have to take in account that it was positive/negative. Thanks a lot...
  13. M

    Can I do this? (integral)

    Hello all, and sorry for making all those threads :shy: I just want to know if I can do this (especially the last part) \int{} \frac{-k\ \lambda \ dx \ x \vec{i} + 2\ k\ \lambda \dx \ \vec{j}}{(x^2 +4)^{3/2}} = \int{} \frac{-k\lambda (x \vec{i} - 2\vec{j}) \ dx}{(x^2 +4)^{3/2}}...
  14. M

    Can you integrate a vector?

    k \lambda \vec{i} \int \frac{dx}{x^2} You mean this? We have just started integrals in math., so I may have confused some things.
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