Tanzalin Method for easier Integration by Parts

[12 Apr 2010]


Here’s a rather neat way to perform certain integrations, where we would normally use Integration by Parts method.

Tanzalin Method can be easier to follow (and could be used to check your work if you have to do Integration by Parts in an examination).

Tanzalin Method is commonly used in Indonesia. I can’t find a reference to it anywhere else (in the English literature) and I couldn’t find any information on Tanzalin, presumably a mathematician.

Example 1

\int2x(3x-2)^6dx

Integration by Parts Method

First, let’s see normal Integration by Parts for comparison.

We identify u, v, du and dv as follows:

u = 2x

dv = (3x − 2)6dx

du = 2dx

v=\frac{1}{21}(3x-2)^7

Integration by Parts then gives us:

\int{udv}=uv-\int{vdu}

\int2x(3x-2)^6dx=\frac{2x}{21}(3x-2)^7-\frac{2}{21}\int(3x-2)^7dx

Now, we find the unknown integral:

\int(3x-2)^7dx=\frac{1}{24}(3x-2)^8+C 

Putting it together, we have:

\int2x(3x-2)^6dx=\frac{2x}{21}(3x-2)^7-\frac{1}{252}(3x-2)^8+C

We can then factor and simplify this to give:

\int2x(3x-2)^6dx=\frac{21x+2}{252}(3x-2)^7+C

The Tanzalin Method is somewhat less messy.

Example 1, now using Tanzalin Method

In the Tanzalin Method, we set up a table as follows. In the first column are successive derivatives of the simplest polynomial term of our integral. (We need to choose this term for the derivatives column because it will disappear after a few steps.)

In the second column are the integrals of the second term of the integral.

We just multiply the 2 terms with green background in the table (the original 2x term and the first integral term). We don’t change the sign of this term.

We then multiply the 2 terms with yellow background (the first derivative and the second integral term). We assign a negative sign to the product, as shown.

The answer for the integral is just the sum of the 2 terms in the final column.

The question again, for reference:

\int2x(3x-2)^6dx

Derivatives Integrals Sign Same-color Products
2x (3x − 2)6    
2 \frac{1}{21}(3x-2)^7 + \frac{2x}{21}(3x-2)^7
0 \frac{1}{504}(3x-2)^8 − -\frac{1}{252}(3x-2)^8

Summing the 4th column:

\int2x(3x-2)^6dx=\frac{2x}{21}(3x-2)^7-\frac{1}{252}(3x-2)^8+C

(We add the constant of integration, C only at the end, not in the table.)

We can then factor and simplify this to give:

\int2x(3x-2)^6dx=\frac{21x+2}{252}(3x-2)^7+C

Example 2

\int{x}\sin{x}\hspace{3}dx

We’ll go straight to the Tanzalin Method.

Derivatives Integrals Sign Same-color Products
x sin x    
1 −cos x + −x cos x
0 −sin x − sin x

We multiplied (x) by (−cos x) and we didn’t change the sign.

We then multiplied (1) by (−sin x) and changed the sign.

Adding the final column gives us the answer:

\int{x}\sin{x}\hspace{3}dx=-x\cos{x}+\sin{x}+C

Example 3

\int{x^2}\sqrt{x-1}\hspace{3}dx 

Using the Tanzalin Method requires 4 rows in the table this time, since there is one more derivative to find in this case.

We need to alternate the signs (3rd column), so our 4th row will have a positive sign.

Derivatives Integrals Sign Same-color Products
x2 (x-1)^\frac{1}{2}    
2x \frac{2}{3}(x-1)^\frac{3}{2} + \frac{2x^2}{3}(x-1)^\frac{3}{2}
2 \large{\frac{4}{15}(x-1)^{\frac{5}{2}}} − \large{-\frac{8x}{15}(x-1)^{\frac{5}{2}}}
0 \large{\frac{8}{105}(x-1)^{\frac{7}{2}}} + \large{\frac{16}{105}(x-1)^{\frac{7}{2}}}

So our final answer is:

{\int{x^2\sqrt{x-1}}dx=}{\frac{2x^2}{3}(x-1)^{\frac{3}{2}}-}{\frac{8x}{15}(x-1)^{\frac{5}{2}}+}{\frac{16}{105}(x-1)^{\frac{7}{2}}}+C

Example 4 – a Problem Arises

This is the same question as Example 3 in the Integration by Parts section in IntMath.

\int{x^2}\ln{4x}\hspace{4}dx

We need to choose ln 4x (natural logarithm of 4x) for the first column this time, following the Integration by Parts priority recommendations of:

  1. log of x,
  2. e raised to power x
  3. x raised to a power

[Note: If we choose the other way round, we would have to find integrals of ln 4x, which is not pretty (and certainly no easier than doing it all using Integration by Parts. See Example 6 on this page: Integration by Parts).

Derivatives Integrals Sign Same-color Products
ln 4x x2    
\frac{1}{x}  \frac{x^3}{3} + \frac{x^3\ln4x}{3}
-\frac{1}{x^2} \frac{x^4}{12} − -\frac{x^3}{12}
\frac{2}{x^3} \frac{x^5}{60} + -\frac{x^3}{60}

When do we stop? The derivatives column will continue to grow, as will the integrals column. The Tanzalin Method requires one of the columns to "disappear" (have value 0) so we have somewhere to stop.

So our final answer is:

\int{x^2}\ln{4x}\hspace{4}dx=\frac{x^3\ln4x}{3}-\left(\frac{1}{12}+\frac{1}{60}+\frac{1}{180}+\frac{1}{420}+\ldots\right)x^3+C

That expression in brackets must equal \frac{1}{9} (since this is the answer we got using Integration by Parts), but as you can see, it is not a Geometric Progression and would take some figuring out.

Conclusion

While Tanzalin Method only handles integrals involving (at least one) polynomial expressions, it is worth considering as a simpler way of writing Integration by Parts questions.

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34 Comments on “Tanzalin Method for easier Integration by Parts”

  1. imran ali says:
    21 Apr 2010 at 7:39 pm [Comment permalink]

    thanx its the better way to solve by parts

    thanx

  2. OKOTH - ODOLLO says:
    21 Apr 2010 at 10:52 pm [Comment permalink]

    Thanks a million. This is very helpful!!!!!!

  3. John Hocutt says:
    22 Apr 2010 at 12:57 am [Comment permalink]

    Great article.

    Turns out that the Tanzalin Method is taught in the US, thought it goes by the name “Tabular Integration by Parts”. Paul Foerster teaches the technique in his text *Calculus Concepts and Applications*. I get no commission for recommending his text, but I’ve found Foerster’s text to be one of the best HS level calculus texts around… When my students were having difficulty with Stewart’s text, I’d often turn to Foerster to clarify the difficulty.

    The approach gives students a terrific way to organize the large volume of intermediate steps that result in a regular integration by parts.

    -Johh Hocutt
    Mr Math & Science

  4. ahmad says:
    22 Apr 2010 at 1:06 am [Comment permalink]

    hi, its a very nice method. Saves time. Its known here in pakistan as the ‘tabular’ method. :)
    A friend taught this to me a week ago but the way you’ve explained it is a lot better!

  5. Kalakay says:
    22 Apr 2010 at 1:55 am [Comment permalink]

    Thanks a lot!
    It was clear (about Tanzalin Method), but I still want to know who is Tanzalin. Please give me a reference!

  6. Murray says:
    22 Apr 2010 at 9:09 am [Comment permalink]

    @John: Thanks for the Foerster recommendation – looks good.

    @Kalakay: As I said, I couldn’t find any reference to him (or her). Can anyone shed light on who this person is?

  7. Salek Raihan says:
    24 Apr 2010 at 5:23 pm [Comment permalink]

    In a word great. Thanks for publishing.

  8. godfrey says:
    25 Apr 2010 at 8:05 pm [Comment permalink]

    great stuff makes me feel like i can create a simpler method. keep the methods cruising guys!

  9. godfrey says:
    25 Apr 2010 at 8:07 pm [Comment permalink]

    is tanzalin alive?

  10. Murray says:
    25 Apr 2010 at 8:42 pm [Comment permalink]

    Hi Godfrey. As I said in the article, I can’t track “Tanzalin” down at all. I don’t even know if it is a person!

    Anyone else know anything?

  11. nandan says:
    26 Apr 2010 at 10:04 pm [Comment permalink]

    wonderful

  12. benjoe says:
    2 May 2010 at 11:04 am [Comment permalink]

    thanks for the stuff guys. but I just wanna know who is tanzalin?

  13. benjoe says:
    2 May 2010 at 11:12 am [Comment permalink]

    The Tanzalin Method is similar to my shortcut method of integration by parts. but my method is much more easy than tanzalin.

  14. DEPR says:
    9 May 2010 at 2:09 pm [Comment permalink]

    its a good way of solving integration by parts, am sure wil find some better solution for the one having no polynomial.

  15. Alan says:
    31 May 2010 at 8:15 am [Comment permalink]

    Thanks for the detailed explanation. One of my book called it as “DI-agonal Method”, which D starts for Differentiate and I as Integrate.

  16. Nick says:
    21 Dec 2010 at 2:35 pm [Comment permalink]

    Thank you very much for this additional method to performing integration by parts!

    I only have one comment to make, and that is that an error in your integral in Example 3 has made two “parts” of the integral be wrong by a factor of two.

    Looking at the table, where it says “2/15(x-1)^(5/2),” it should read “4/15…” with the same thing.

    I just thought I should clarify, just in case someone comes in and is learning integration fresh and gets a bit confused.

    EXCELLENT work, though. Really. This and all the other integral articles you have are extremely easy to understand and thorough. Nice job.

  17. Murray says:
    21 Dec 2010 at 5:20 pm [Comment permalink]

    Hi Nick. You are so right! I amended the post and fixed the flow-on errors as well.

    Thanks for the helpful feedback.

  18. Peter Mulendema says:
    28 Feb 2011 at 11:39 pm [Comment permalink]

    Hi
    The Integration method shown is wonderfull. It made me feel happy and like maths even more. This web is very exciting and knowledge building. i will always be a memmber. Keep it up.

  19. Lik Mie says:
    12 Apr 2011 at 12:30 pm [Comment permalink]

    Hay. You method integration become take eassy and I always be a member.Sip nice god job

  20. Servantone says:
    20 Apr 2011 at 1:59 pm [Comment permalink]

    xample 6 on this page: Integration by Parts).

    sign diff. int wt x

    + —-> ln 4x —-> x^2 horizontlly +int x^2ln4x dx

    – —-> 1/x —-> x^3/3 horizontlly -int 1/x(x^3/3)dx

    diagonal +(\ln 4x)(x^3/3)
    stop stop stop

    It can be written as

    +int x^2ln4x dx=(\ln 4x)(x^3/3)-int 1/x(x^3/3)dx
    =(\ln 4x)(x^3/3)-int(x^2/3)dx
    =(\ln 4x)(x^3/3)-x^3/9)+C.

  21. Murray says:
    20 Apr 2011 at 9:41 pm [Comment permalink]

    @Servantone: I think you mean Example 3 on the Integration by Parts page.

    Thanks for your input!

  22. pascal tambo thomas says:
    10 May 2011 at 9:49 pm [Comment permalink]

    question:integrate sin^2x using method of integration by parts

  23. Leke Olusegun says:
    16 Jun 2011 at 12:55 pm [Comment permalink]

    I really love dis method.I think i will go and teach it to my friends here in the university of Benin,Benin city.Nigeria..Thanks a million

  24. 123 says:
    23 Jul 2011 at 10:53 pm [Comment permalink]

    intergral lnx=

  25. Murray says:
    24 Jul 2011 at 12:21 pm [Comment permalink]

    @ “123″: This page is linked to in the article: Integration by Parts, and Example 6 covers your question.

  26. Murray says:
    10 Aug 2011 at 3:55 pm [Comment permalink]

    Hi Pascal. This is one way to do it: Wolfram]Alpha’s solution (although they are not using integration by parts)

  27. saed says:
    28 Nov 2011 at 11:23 pm [Comment permalink]

    it is very easy for us.but this way has been not mark by tacher.thanks

  28. Murray says:
    29 Nov 2011 at 2:13 pm [Comment permalink]

    @Saed: That is sad to hear, Saed. Students need to do the same number of differentiations and integrations as the normal method, but it’s just easier to follow.

    Perhaps you could send your teacher the link to this article and maybe they might change their mind?

  29. Murray says:
    29 Nov 2011 at 2:13 pm [Comment permalink]

    @Saed: That is sad to hear, Saed. Students need to do the same number of differentiations and integrations as the normal method, but it’s just easier to follow.

    Perhaps you could send your teacher the link to this article and maybe they might change their mind?

  30. vijay kachhadiya says:
    2 Feb 2012 at 6:20 pm [Comment permalink]

    Oh !!!! That’s much much easier than the integration by parts ..

    I will definately teach this method to my students in my class…

    Thank u very much ….!

  31. Richard says:
    10 Feb 2012 at 11:41 pm [Comment permalink]

    This is excellent but I think it would be well worth mentioning that this method does not “only handle integrals involving (at least one) polynomial expressions”–it does!

    In example 4, you can stop at line 2 and treat the integral of the product of the terms as the “remainder” term. In general, any time the product of two columns is something easily integrable (not in my spell checker) you can stop and take the integral.

    Nicely worked examples using this (tabular) method here: http://www.mccd.edu/faculty/powerd/M4b/M4b_L3_IBP.htm

    This method also works for Int (e^x sin(x)) when you realize that the 3rd line is the same as the 1st.

  32. Murray says:
    11 Feb 2012 at 11:49 am [Comment permalink]

    @Richard: Thanks for the comments – and for the extra resource.

  33. roel says:
    20 Mar 2012 at 6:15 pm [Comment permalink]

    there another method. it the same as the original, but it lets you write everything in one step. i have not seen it on any other page
    integral(uv)=u*integral(v)-integral[integral(v)*derivative(u)]dx
    if some one can write this in a clearer form, please do

  34. Murray says:
    24 Mar 2012 at 5:13 pm [Comment permalink]

    @Roel – Yes, that’s the standard way of writing integration by parts. Tanzalin Method is somewhat more systematic and probably easier to follow for many students.

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