Solving cos^3 x dx: A Quick and Easy Method

  • Context: Undergrad 
  • Thread starter Thread starter PrudensOptimus
  • Start date Start date
  • Tags Tags
    Dx
Click For Summary

Discussion Overview

The discussion revolves around the integration of the function cos3x dx, exploring various methods and techniques for solving the integral. Participants share their approaches, clarify terminology, and express their understanding of integration concepts, particularly substitution and integration by parts.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant claims the solution for the integral is sinx - sin3x / 3 + C, suggesting a method involving the integral of cosx*(1-sin2x) dx.
  • Another participant points out the need for clarity in stating that the task is to integrate, implying that terminology matters in mathematical discussions.
  • A participant suggests that distributing the multiplication might provide hints for solving the integral, while another counters that substitution is a more straightforward approach.
  • Some participants express varying levels of familiarity with integration techniques, with one stating they have not learned integration by parts and another questioning their understanding of substitution.
  • One participant shares a link to their worked-out solution, indicating an attempt to illustrate their process for integrating the function.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best method for integrating cos3x dx, with differing opinions on whether to use substitution or distribution. Additionally, there is a lack of agreement on the participants' familiarity with integration techniques, leading to varied levels of understanding and approach.

Contextual Notes

Some participants express confusion about specific steps in integration, such as the use of dx = dv(ax), indicating potential gaps in understanding or missing foundational knowledge in integration techniques.

Who May Find This Useful

This discussion may be useful for students learning integration techniques, particularly those unfamiliar with substitution and integration by parts, as well as those seeking clarification on the integration of trigonometric functions.

PrudensOptimus
Messages
641
Reaction score
0
OK, I know the solution for cos^3 x dx is sinx - sin^3 x / 3 + C.


And that

you basically solve

integral of cosx*(1-sin^2x) dx. to get it.

but,...

what I don't get is how do you solve cosx*(1-sin^x) dx... is there a trick that I didn't get from the parts formula?
 
Physics news on Phys.org
It would help if you mentioned you're trying to integrate!

Distribute the multiplication and see if that gives you any hints.
 
Yes, one doesn't normally say "solve f(x)dx"!

Hurkyl, I don't see any reason to "distribute" (multiply out) anything. There is an obvious substitution for ∫(1- sin2(x))cos(x)dx.
 
Good point. :smile:
 
I have never learned integration by parts. Please help me.
 
But, I presume, you know substitution?
 
Nope, any products in Integrals other than those constants are new to me.
 
I didn't ask about products, I asked about substitution!


E.G. would you know how to integrate ∫ sin(πx) dx
 
i know the answer,

but I don't know the part when they did the dx = dv(ax) part... that confuzed me.
 
  • #10
Ok well here's how I worked it out

http://myfiles.dyndns.org/pictures/integrate1.jpg

I put a few steps together but you can still see what happened sort of.
 
Last edited by a moderator:

Similar threads

  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 4 ·
Replies
4
Views
3K
Replies
5
Views
5K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 12 ·
Replies
12
Views
4K
  • · Replies 4 ·
Replies
4
Views
5K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 27 ·
Replies
27
Views
4K