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Help with IntegralS! Very Important! Quick!

  1. May 5, 2007 #1
    Hi! I`m poor student from Ukraine! I`m writing u becouse u are my last chans!
    So I need to do homewofk for monday-tuesday. I have problem becouse i was ill and siting at home during lessons about integration! Sorry for My bad English, but i hope u understad.
    So i have 10 integrals! At first i search in intarnet some calcus. I found www.cal101.com But it give me only result. Function step by step only for money! But i haven`t! what i must do? =( Thanks God and Google I find U.
    I hope u help me becouse it`s very very important to me.
    So 10 integrals(all indefine):
    1) (2*(x^(1/3))+3*x*(x^(1/2)))/(x^(1/4))
    2) ((x^3+1)^(1/4))*(x^2)
    3) (1-2*sinx)/(cosx^2)
    4) 2^(x/2)
    5) dx/((4-x^2)^(1/2))
    6) tg(x^(1/2))*(dx/x^(1/2))
    7) dx/((4+x^2)^(1/2))
    8) (sin(x/2))^2
    9) lnx/(x^(1/2))
    10) (1-3x)cos2x
    They are in Attach Files!
     

    Attached Files:

  2. jcsd
  3. May 5, 2007 #2

    cristo

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    Hi and welcome to the forums. Firstly please note that the forum rules state that you must show some work before we can help. What do you know about integration? Have you had a go at any of the questions?

    Also, in future, please note that we have homework forums specifically for these type of question.
     
  4. May 5, 2007 #3
    I agree with u, - I must do homework not u. I`ve just start so in atach u can see 1 an 2 . But i think it isn`t right/
     

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  5. May 5, 2007 #4

    cristo

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    1. [tex]x\sqrt{x}=x\cdot x^{1/2}=x^{3/2}[/tex]

    2. Your technique is incorrect. Have you come across integration by substitution? Try the substitution y=x^3+1
     
  6. May 5, 2007 #5
    U know if i weren`t ill all 2 week, i do home work well. I`m have good marks 87 of 100. I have never ask people to help me in algebra.. butt know. very X situation. I haven`t free time to learn intaegrals, becouse now i do years work in Descrete Mathematic. =( Next week i must to complete. Thanks God with Descrete mathematica i`m good.
     
  7. May 5, 2007 #6
    O fu.... Really. It`s child mistake... Oh.... Sorry. Hm . I`m trying again.
     
  8. May 5, 2007 #7

    cristo

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    Ok. Don't worry, and don't let youself get stressed; it's only homework, not a life and death situation! Try and calm down a little, and take your time. Then you're less likely to make mistakes.
     
  9. May 5, 2007 #8
    About 1. I`m stuck in a middle. I have result (72x^(13/12))+(52x^(9/4)))/39. Is it right?
    About 2. I don`t under stand explain me please.
     
  10. May 5, 2007 #9
    You know i do right the 1st =) I compare it with cal101 result. Cal101 make other version but in result we have right rsult =) He he I love integrals!
     
  11. May 5, 2007 #10
    But.. Remain else 9 . What to do?
     
  12. May 5, 2007 #11
    ANd u now... U have 3 pm. But i`m in 0.13 AM =( Really want go to sleep but How? =( when i think, what will hapen with me if i will not complete the task....
     
  13. May 5, 2007 #12
    About the 2. In calc101.com result (atach file) diferent only with x^3 (see my version) . So where i do mistake , and in the and have misterios x^3
     

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  14. May 5, 2007 #13
    How did you get in this bad situation?
     
  15. May 5, 2007 #14
    I much powerfully was ill, and has missed nearly 2 weeks lessons. Beside me was a temperature from 35.6 before 39. ANd i couldn`t do anything.
     
  16. May 5, 2007 #15

    cristo

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    Right: question 1. [tex]\int\frac{2x^{1/3}+3x^{3/2}}{x^{1/4}}dx=\int 2x^{1/2}+3x^{5/4} dx [/tex] Can you integrate this using the rule for fractional powers?

    question 2. [itex]\int(x^3+1)^{1/4}x^2 dx[/itex].
    Are you familiar with the method of substitution? If so use the substitution y=x^3+1; this gives dy=3x^2dx. Substituting into the integrand gives [tex]\int y^{1/4}\frac{dy}{3}[/tex]. Can you solve this? The substituting in for x will give you the solution.
     
  17. May 5, 2007 #16

    cristo

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    A few more hints for the ones I can see how to do immediately!

    5&7 will be some trig subsitutions. For 5 let x=2sinu, for 7 let x=2tanu.
    8. looks like it will be do-able using the double angle formula to express it in terms of sinx (or cosx)
    10. use integration by parts.

    That should give you a bit to work on, I'll have a look at the others in more detail when I've got time [or if anyone else is reading, feel free to help, of course!!!]
     
  18. May 5, 2007 #17
    How much do you know about integration?
     
  19. May 6, 2007 #18
    To Crosson:
    Not much. =(. But I trying to rescue the situation.
    I`ve just get up. Now i start to do the second. And when i finish it, try to make 5&7.
     
  20. May 6, 2007 #19
    THX . I `ve done the second! Integration is interesting .... but.. now i just start to do 5... =9
     
  21. May 6, 2007 #20
    Hm see the 5. I can`t stand, what i do wrong. help:confused:
     

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