How to Find the Indefinite Integral of sin(pi x) dx?

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Discussion Overview

The discussion revolves around finding the indefinite integral of the function sin(πx) dx. Participants explore different approaches to the integration process, including substitution methods and the application of the chain rule.

Discussion Character

  • Mathematical reasoning

Main Points Raised

  • One participant suggests that the integral might be -cos(πx) dx, but is uncertain and considers the possibility of it being (1/π) - cos(πx) dx.
  • Another participant presents a substitution method, stating that the integral can be expressed as (1/π) ∫ sin(πx) d(πx), questioning if this approach is helpful.
  • A participant expresses gratitude for the confirmation of their initial guess regarding the integral but remains unsure about its correctness.
  • One participant questions the reason for the (1/π) factor, indicating a lack of understanding about its necessity.
  • A participant asks for the derivative of cos(πx), which leads to the response that it is -sin(πx).
  • Another participant asserts that the derivative is not -sin(πx), suggesting the use of the chain rule instead.
  • A suggestion is made to consider a substitution of u = πx to facilitate the integration process.

Areas of Agreement / Disagreement

Participants express differing views on the correct form of the integral and the role of the (1/π) factor, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

Some participants exhibit uncertainty regarding the application of the chain rule and the substitution method, highlighting potential gaps in understanding the integration process.

afcwestwarrior
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of sin pi x dx

i thought it would be - cos pi x dx but i think it might be (1/pi) -cos pi x dx
 
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\int \sin (\pi x)\, \mathrm{d}x =\frac{1}{\pi} \int \sin (\pi x) \, \mathrm{d} (\pi x)

Does this help?
 
yea a lot thanks, i guessed right but i didn't know if i was right
 
just wondering why is it 1/pi, I'm not even sure why
 
What is the derivative of cos(pi x)?
 
it's - sin (pi x)
 
To integrate sin( \pi x) dx consider doing a substitution of u = \pi x then substitute in the appropriate expression of dx in terms of du.
 
afcwestwarrior said:
it's - sin (pi x)
Well, there is you problem then: it isn't. Use the chain rule.
 
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