Integral Problem Help

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Chris686

New member
Joined
Sep 1, 2012
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19
I'm doing the integral of:

cos2xsinxdx

I get u = cosx
du = -sinx
-du = sinx

so

-U3/3 + C

I'm pretty certain this is correct, but the professor put up the same solution without the negative sign. Does the negative belong, or not?
 
Chris686 said:
I'm doing the integral of:

cos2xsinxdx

\(\displaystyle \displaystyle\int cos^2(x)sin(x)dx\)

I get u = cosx
du = -sinx dx . . . . You must have the "dx" for these two lines of work.
-du = sinx dx

so

-U3/3 + C . . . . Keep it the same lower case as shown below.

\(\displaystyle -u^3/3 + C\)

I'm pretty certain this is correct,
Yours is correct so far. And then there would be the substituting back to finish the problem.

but the professor put up the same solution without the negative sign.

Does the negative belong, or not?
Yes, it is, on the condition that you posted the problem correctly.
Click to expand...

...
 
Thanks for the response. I was certain I was doing it correctly, but I wanted to make sure since my final is tomorrow. Yes, it's the correct problem, and I knew how to finish. You just wouldn't believe how many errors this professor makes :)

I am bad about putting in dx and the various calculus symbols. I'm trying to get into a better habit of doing so, but it's easy to overlook.

Also, how am I able to make my posts more readable, like yours? I've checked the stickies, and I don't see any tutorials. I'd like to know, since I'll likely post a problem or two for help next semester for Calc 2, and it's just much easier on the eyes. :wink:
 
Chris686 said:
how am I able to make my posts more readable, like yours? I've checked the stickies, and I don't see any tutorials. I'd like to know, since I'll likely post a problem or two for help next semester for Calc 2, and it's just much easier on the eyes. :wink:
Click to expand...
If you are going to post only a few problems, it is probably not worthwhile to learn LaTex, which is the method used on this site to render mathematical statements in a very readable form.

I taught myself basic LaTex through two sources.

The primary one was by imitating others on this site. If you hit reply with quote to a posting on this site with LaTex in it, you will see the actual code used to produce Latex. For example, if you hit reply with quote to this posting, you will see how I did this:

\(\displaystyle \displaystyle \left(\sum_{i=1}^n\dfrac{r * P}{(1 + r)^i}\right) + \dfrac{P}{(1 + r)^n}\)

A number of posters here, such as soroban, are able to do amazing things with LaTex.

Once you have a some idea of how LaTex works, I found this site to be very helpful:

http://www.artofproblemsolving.com/Wiki/index.php/LaTeX:Symbols

As I said, however, I greatly doubt that it is worth the effort to learn for only a few posts.
 
Jeff, those are exactly the two main resources I used when learning to use \(\displaystyle \LaTeX\)! :cool:
 
JeffM said:
\(\displaystyle \displaystyle \left(\sum_{i=1}^n\dfrac{r * P}{(1 + r)^i}\right) + \dfrac{P}{(1 + r)^n}\)

Once you have a some idea of how LaTex works, I found this site to be very helpful:

http://www.artofproblemsolving.com/Wiki/index.php/LaTeX:Symbols
Click to expand...

Thanks Jeff - I haven't previously programmed LaTeX, but I am familiar with the concepts, and html tags. That list of Symbols is essential! I am also looking at a tutorial,

http://www.maths.tcd.ie/~dwilkins/LaTeXPrimer
 
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