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integrate wrt x: (1/x)*logx?

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  • 1 decade ago
    Favorite Answer

    (1/x)*logx*dx

    = logx d(logx)

    on integration

    =1/2 (logx)^2 + C

  • 1 decade ago

    you can write it as integral of logx*(1/x)dx. I am assuming its a natural log.

    now as u can see derivative of logx (i.e 1/x) is invloved in integral thus u can apply power rule of integration.

    solution is

    integral of logx*1/x*dx ------(A)

    substitue t=logx

    now dt=1/x*dx

    now statement A will look like this

    integral of t*dt

    on integrating you will get t^2 + C

    now putting back the value of 't' will yield you

    ((logx)^2)/2 +c

    n tht's ur answer!!!!

  • 1 decade ago

    Substitute logx=t. diffrentiating, we get (1/x)dx=dt. Therefore the integrand becomes t.dt, whose integral is (t^2)/2 + c. Back substituting t as logx, we have the solution as (logx)^2/2 +c.

  • the given qty is logx (1/x)dx

    = logx d(logx)

    Integral = (1/2)*(logx)^2

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  • Puggy
    Lv 7
    1 decade ago

    Integral ( (1/x)log[base 10](x) )dx

    {Note: By log(x), I'm going to assume base 10, the same way a calculator does. I'm NOT going to assume log[base e], because there's already an assigned function for that; ln}

    I'm going to change the form of that slightly, so I can show you how the substitution is done.

    Integral (log(x) (1/x)dx)

    Before we perform our substitution, remember that the derivative of log[base a](x) is 1/[xln(a)]. It looks similar to the derivative of

    ln(x) except it's multiplied by 1/ln(a).

    Let u = log(x). Then

    du = 1/[x ln(10)] dx

    Multiplying both sides by ln(10), we have

    ln(10) du = (1/x) dx

    Note that we can now directly replace (1/x) dx with ln(10) du. The result of our substitution is then:

    Integral (log(x) (1/x)dx) becomes

    Integral (u (ln 10) du)

    Let's pull out the constant ln 10 out of the integral.

    (ln10) * Integral (u du)

    And now, it's straightforward reverse power rule.

    (ln10) * (1/2)u^2 + C

    Substituting in u = log(x) back, we have

    (ln10) * (1/2) (log(x))^2 + C

    Simplifying this slightly,

    [(ln10)/2] * [log(x)]^2 + C

  • Helmut
    Lv 7
    1 decade ago

    ∫(1/x)*logxdx

    let u = logx

    du = dx/x

    ∫(1/x)*logxdx = udu = (1/2)u^2 + C

    ∫(1/x)*logxdx = (1/2)(logx)^2 + C

  • maussy
    Lv 7
    1 decade ago

    First log x = ln x /ln10 , so wrt x = 1/ln10 *(1/x) *lnx

    if you put u = lnx i/x *dx =du

    so you must integer (1/ln10 ) udu

    integration of udu is u^2/2

    and the result of the integration is (1/2*ln10) (lnx)^2

  • put logx=t

    1/x dx=dt;

    it simply reduces to integral tdt which is t^2/2 +c

    The answer is (logx)^2/2+c

  • 1 decade ago

    assume In(x)=t, we have d(Inx)/dx=1/x so 1/x * dx =d(Inx)

    so Integrate (1/x)* logx .wrt.x = Integ( 1/x) * Inx/ In(10) .wrt.x

    as Integ (1/x) * Inx .wrt.x=integ Inx wrt.(Inx)

    so Integ (1/x) * inx. wrt.x = integ t wrt. t = 0.5 t * t

    as In (x) = t so

    ur question = 0.5 (in(x) * In(x))/ In(10)

  • 1 decade ago

    Integrate (1/x)(ln x). I assume you mean the natural log.

    ∫(1/x)(ln x)dx

    Let

    u = ln x

    du = (1/x)dx

    ∫(1/x)(ln x)dx = ∫u(du) = u²/2 + C = (ln x)²/2 + C

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