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It's my first post here and I was wondering if someone could help me with evaluating the definite integral $$ \int_0^{\Large\frac{\pi}{4}} \log\left( \cos x\right) \, \mathrm{d}x $$ Thanks in advance, any help would be appreciated.

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    What did you try ? maybe putting $t=\cos(x)$ would help2012-09-19
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    There is an answer, but I cannot say how it is found: http://www.wolframalpha.com/input/?i=Integrate[Log[Cos[x]]%2C{x%2C0%2CPi%2F4}]2012-09-19
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    @Siminore: That link is broken; [here](http://wolframalpha.com/input/?i=Integrate[Log[Cos[x]]%2C{x%2C0%2CPi%2F4}])'s one that works.2012-09-19
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    @Souvik : You mean 'evaluating'.2012-09-19

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