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  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.
  15. M

    Can you integrate a vector?

    It is -i , since they ask the electric field at x=0 . Is there a reason you are asking this?
  16. M

    Can you integrate a vector?

    Hello, I just wanted to know if you can integrate a vector, and if so, how. Here is a problem: A charged piece of metal of linear density 2 * 10^-6 * x , between x=2 and x=5. I found its charge by integrating.. and it is 21 micro C. Now that's what I want to know: calculate the electric...
  17. M

    Coulomb's law vector question.

    When I solve for x and y , I get x= (+-) 3,16 and y= 1,27 ... Anyway, I already understood your first method, it's a lot more easier.. but I dont know why it never works like you have written. Thanks a lot for all your time and help, Healey01 :)
  18. M

    Coulomb's law vector question.

    Thanks a lot Healey01, I understand . :cool: What I don't get is the teacher told me to equal the i and j vectors so it makes two different equations, and since I have 2 unknown values, I'd find them like that. Do you have any idea how to do that? I tried ( 0,222 \vec{i} + 0,250\vec{j})...
  19. M

    Coulomb's law vector question.

    That is the right answer, except it's (-1,8 i - 2,05j) (no problem there) I just want to know from where comes the 0,3343(0,66399\vec{i} + 0,7477\vec{j}) = 0,3343\vec{u_{21}} Thanks a lot for the help, can you just clarify this for me? :)
  20. M

    Coulomb's law vector question.

    I still haven't received an answer for this one :P . I'll check tomorrow with my teacher. I'm in my 2nd session, and my cote R from the first one is great, so if I can continue like that, maybe next year I can make an admission. :) Thanks bro
  21. M

    Coulomb's law vector question.

    I think the only Charbonneau there is named Pierre Charbonneau..
  22. M

    Coulomb's law vector question.

    Bois-de-Boulogne. What program are you in now? I want to enter UdeM in medecine
  23. M

    Coulomb's law vector question.

    Exactly :) And I'm not in Europe ;) in Montreal , Canada
  24. M

    Coulomb's law vector question.

    yes, decimals, as in 2 and a half Q
  25. M

    Coulomb's law vector question.

    Sorry for the question, I posted the one they asked but forgot to add that they're ponctual charges. It's in french, that's why I translated it. But basically, the two charges create a resultant force of the one I wrote in my post. They then ask where to put a ponctual 2,5Q charge to nullfy the...
  26. M

    Coulomb's law vector question.

    I have been using vectors with units for over a year in my physics courses. Every teacher in the physics department teaches this. A force has components in i, j and k.. how can it not have units? But I dont want to start an argument here about this, that's what we use here. Thanks for pointing...
  27. M

    Coulomb's law vector question.

    Yes, that's how I started the problem, but it gives me a wrong answer..
  28. M

    Coulomb's law vector question.

    A force has a unit, Newtons, that's why I posted the N.It has a force in a direction i and j. Healey01, thanks for the help but that's not the answer. The question was there's two charge that create a force (the first one I posted) on another charge. They then add a 2,5Q charge and ask...
  29. M

    Coulomb's law vector question.

    Hello, I have a simple exercice I'm having trouble to solve. So we have a) and b) a) asked the force applied on a charge.... and the answer was \vec{F_{res}.}= Qkq ( -0,222 \vec{i} -0,250\vec{j}) N that's not a problem here.. that was the good answer. Now in b), they're asking where...
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