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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]

*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]

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 [Broken]

[/URL]*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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