Find Where Y=cosx is Decreasing: -π to π

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Homework Help Overview

The discussion revolves around determining the intervals where the function y = cos(x) is decreasing within the range of -π to π. Participants are examining the correctness of answers provided in a textbook and discussing the implications of those answers.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants are questioning the intervals provided by the textbook, with some suggesting that the correct interval for decreasing values might be different than what is stated. There is also a mention of confusion regarding the transition to a different question.

Discussion Status

The conversation reflects uncertainty about the textbook's accuracy, with multiple participants expressing doubt about the provided answers. There is no clear consensus, but the discussion is active with participants seeking clarification.

Contextual Notes

Participants note discrepancies between the textbook's answers and their own interpretations, particularly regarding the specified interval for the function's behavior. There is an acknowledgment of a shift in focus to a different question during the discussion.

rocomath
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Hmm ... I did this problem for a friend.

From what x values is [tex]y=cos x[/tex] decreasing from [tex]-\pi\leq x\leq\pi[/tex]

http://img440.imageshack.us/img440/3876/baocu5.jpg​
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*it should be [tex]-\frac{\pi}{2} \ \mbox{not} \ -\frac{3\pi}{2}[/tex]

It's decreasing from [tex](0,\pi)[/tex] but the answer she gave me from the back of the book is [tex]-\frac{3\pi}{2}<x<\frac{3\pi}{2}[/tex]
 
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Nvm ... we apparently moved onto a different question, lol.
 
The book's wrong
 
Must be some of that new math :confused:
 
Feldoh said:
The book's wrong
LOL, no she started asking about a different question ... I just didn't realize, ha. I was like wtf ... b/c the answer she gave me wasn't even in the interval they were asking about! haha, I kept saying no it's wrong! And I'll prove it by asking the PF Gods :)
 
It looks a bit weird when it askes for the answer on the interval [-pi,pi] the books gives the answer as [-1.5pi,1.5pi]
 

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