$\begin{gathered}
\left. \begin{gathered}
E\hat CM = E\hat AL \hfill \\
\frac{{CM}}
{{AL}} = \frac{{BC}}
{{AC}} = \frac{{EC}}
{{EA}} \hfill \\
\end{gathered} \right\}\mathop {}\limits_{}^{} \Rightarrow \mathop {}\limits_{}^{} \left\{ \begin{gathered}
E\hat CM = E\hat AL \hfill \\
\frac{{CM}}
{{AL}} = \frac{{EC}}
{{EA}} \hfill \\
\end{gathered} \right.\mathop {}\limits_{}^{} \Rightarrow \mathop {}\limits_{}^{} ECM\mathop {}\limits_{}^{} \approx \mathop {}\limits_{}^{} EAL\mathop {}\limits_{}^{} \Rightarrow \mathop {}\limits_{}^{} C\hat EM = A\hat EL\mathop {}\limits_{}^{} ,\mathop {}\limits_{}^{} (1) \hfill \\
B\hat HE = E\hat AC\mathop {}\limits_{}^{} \Rightarrow \mathop {}\limits_{}^{\mathop {}\limits_{}^{} } E\hat OC\mathop {}\limits_{}^{} \Rightarrow \mathop {}\limits_{}^{} H\hat EO = 90^O \mathop {}\limits_{}^{} \mathop \Rightarrow \limits^{(1)} \mathop {}\limits_{}^{} M\hat EL = 90^O \hfill \\
\end{gathered} $
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