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Antonache Emanuel
Euclid
Posts: 37
Joined: Sat Feb 28, 2009 4:15 pm
Location: Targoviste, Dambovita

Shortlist 14

Post by Antonache Emanuel »

Demostrati ca pentru orice numere reale x,y, avem:
\( |cosx|+|cosy|+|cos(x+y)|\ge1 \).
Dorin Arventiev, Constanta, Shortlist 2003
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Marius Mainea
Gauss
Posts: 1077
Joined: Mon May 26, 2008 2:12 pm
Location: Gaesti (Dambovita)

Post by Marius Mainea »

Se reduce la \( |\cos x|+|\cos y|+|\cos z|\ge |\cos (x+y+z)| \) unde \( x+y+z=0 \)
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