Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Wolfram Alpha:

I'll probably kick myself when someone explains it, but I can't understand where the 1/12 comes from after the re-substitution of u? I thought it would be 1/3, but it clearly isn't. Why is that?

Thanks for input on this.

share|improve this question
Just a word of warning: using Wolfram Alpha should be limited to checking answers (if it is used at all). I personally believe WA is a crutch that actually undermines ones ability to understand calculus fully. You have asked a few questions concerning standard trig-substitution. I would suggest that with this type of problem you put away the computer (math.se and WA alike), sit down with a sheet of paper and try as many examples from a textbook as you can. –  JavaMan Aug 30 '11 at 3:14
Ok. I thought since it explained the steps it was better than not having someone to consult with questions, but I'll follow your advice then. Thanks. –  rkMathUser Aug 30 '11 at 3:26
add comment

1 Answer

up vote 1 down vote accepted

Since x is cubed, when the 1/2 is factored it turns into 1/8. Then 2/3 times 1/8 is 1/12.

share|improve this answer
Makes perfect sense now. Thanks –  rkMathUser Aug 30 '11 at 3:27
add comment

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.