Inegalitate cu sin x , cos x

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alex2008
Leibniz
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Joined: Sun Oct 19, 2008 3:23 pm
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Inegalitate cu sin x , cos x

Post by alex2008 »

Aratati ca
\( \frac{1}{sin^4x}+\frac{1}{cos^4x}\ge 8 \) \( (\forall)x\neq k\cdot \frac{\pi}{2} \)
. A snake that slithers on the ground can only dream of flying through the air.
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mihai++
Bernoulli
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Joined: Wed Nov 28, 2007 8:08 pm
Location: Focsani

Post by mihai++ »

\( \frac{1}{x^4}+\frac{1}{y^4}\geq \frac{4}{x^4+y^4}\geq\frac{8}{(x^2+y^2)^2}=8. \)
n-ar fi rau sa fie bine :)
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