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Dan Barbilian 2008

Posted: Sun Jan 11, 2009 3:09 pm
by andy crisan
Sa se arate ca in orice triunghi are loc relatia.
\( 2^a+2^b+2^c>2^m^a+2^m^b+2^m^c \), notatiile fiind cele cunoscute.

Posted: Sun Jan 11, 2009 6:02 pm
by mihai++
avem \( \sum2^a=\sum\frac{2^a+2^b}{2}\geq\sum2^{\frac{a+b}{2}}>\sum2^{m_c} \), deoarece:
\( m_c^2=\frac{2(a^2+b^2)-c^2}{4}\leq\frac{2(a^2+b^2)-(a-b)^2}{4}=(\frac{a+b}{2})^2 \).