\(\begin{align}
& {{A}_{1}}P\le PD \\
& △ {{A}_{1}}PF\le △ DPF \\
\end{align}\)
同理
\(\begin{align}
& △ {{B}_{1}}QD\le △ EQD \\
& △ {{C}_{1}}RE\le △ FRE \\
\end{align}\)
\(\begin{align}
& △ {{A}_{1}}{{B}_{1}}{{C}_{1}}-DPFREQ\le DPFREQ-△ DEF\le DPFREQ \\
& DPFREQ\ge \frac{△ {{A}_{1}}{{B}_{1}}{{C}_{1}}}{2}=\frac{1}{8} \\
\end{align}\)
附件
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20140611_2.jpg
(32.18 KB)
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2014-6-11 22:45
