[tex]\bf \Delta ABC,\ cu\ \mathcal{A}-aria,\ BC=a,\ h_a\ -\ \hat\imath n\breve al\c{t}imea\ corespunz\breved atoare\ lui\ BC\\ \\ \\ \it \mathcal{A}=\dfrac{a\cdot h_a}{2} \Rightarrow \begin{cases} \it h_a=\dfrac{2\cdot\mathcal{A}}{a}\\ \\ \\ \it a=\dfrac{2\cdot\mathcal{A}}{h_{a}}\end{cases}[/tex]
a)
[tex]\it \mathcal{A}=\dfrac{5,5\cdot4}{2}=\dfrac{22}{2}=11\ cm^2[/tex]
d)
[tex]\it a=\dfrac{2\cdot56}{8}=2\cdot7=14\ cm[/tex]
