[tex]\it a) Din\ triunghiul\ EBC,\ dreptunghic,\ m(\hat E)=90^o,\ \Rightarrow cosB=\dfrac{EB}{BC}\ \ \ \ \ (1)\\ \\ Dar,\ \ cosB=0,6=\dfrac{\ 6^{(2}}{10}=\dfrac{3}{5}\ \ \ \ \ (2)\\ \\ (1),\ (2) \Rightarrow \dfrac{EB}{BC}= \dfrac{3}{5}\Rightarrow \begin{cases}\it EB=3k\\ \\ BC=5k\end{cases},\ \ k\in\matbb{R}\ \ \ \ \ (3)[/tex]
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