A sin^2 and cos^2 integrals question

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    Integrals
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Discussion Overview

The discussion centers on the evaluation of definite integrals involving the squares of sine and cosine functions, specifically questioning the results over various intervals. Participants explore the implications of averaging these functions and the effects of different integration limits.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant questions whether the definite integral of [sin(x)]^2 from 0 to a equals a/2, and similarly for cos(x).
  • Another participant challenges the assertion that the average value of sine and cosine functions is always 1/2, indicating that this is not the case.
  • There is a query about whether the integration region affects the results, particularly for intervals such as -a to a and -3a to 0.5a.
  • A participant recalls a teacher stating that the integral of squared sine or cosine is always 1/2, seeking clarification on the validity of this claim and the applicable ranges.
  • Another participant asserts that the simple calculations of the integrals do not yield the proposed results, implying a need for further understanding of integral calculus.
  • One participant mentions finding a formula online for the integrals, suggesting a reliance on external resources for answers.

Areas of Agreement / Disagreement

Participants express disagreement regarding the results of the integrals and the average values of sine and cosine functions. There is no consensus on the correctness of the initial claims or the implications of the integration limits.

Contextual Notes

Participants have not resolved the mathematical steps involved in the integrals, and there are uncertainties regarding the conditions under which the average values hold true.

dudinka
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hi!

1. Is the definite integral over [sin(x)]^2 from 0 to a, is a/2? and also the cosine?

2. Is it because the average of the sin/cos functions is always 1/2?

3. and if so, the integration region doesn't matter because the function is positive?
I mean, what about integration from -a to a?

4. and from -3a to 0.5a? is it: 0.5*[3.5a]?

thanks!
 
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Well, for 1. why do you ask us ? Can't you compute it all by yourself ? The answer is "no", btw. Then you can figure out the aswers to the other questions. And the average of the sin/cos in not always 1/2.
 
are you trying to help?

I'm asking because I don't know the answers.
 
Well, the simple calculation of those 2 integrals doesn't yield the results you proposed. So do you know anything about integral calculus ? I'm asking because the answer will make me post the solutions to those integrals or not...
 
I've just found a formula on the net for those integrals, thnks anyway.

but I remember my teacher said that integral over squared(!) sin/cos is always 1/2 or something.
Is this correct? if so, for what range?
 
Nope, of course not. The range can be let's say for the cos^2 from 0 to the solution of the equation 2a+sin 2a=2.
 
thanks!
 

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