[tex]\boxed{\begin{array}{l}\rm 1)\\\sf p=\dfrac{15+13+8}{2}=\dfrac{36}{2}=18\\\sf A=\sqrt{18\cdot(18-15)\cdot(18-13)\cdot(18-8)}\\\sf A=\sqrt{18\cdot3\cdot5\cdot10}\\\sf A=\sqrt{2\cdot9\cdot3\cdot5\cdot2\cdot5}\\\sf A=\sqrt{4\cdot9\cdot25\cdot3}\\\sf A=2\cdot3\cdot5\sqrt{3}\\\sf A=30\sqrt{3}\\\sf A=30\cdot1,732\\\sf A=51,96~cm^2\end{array}}[/tex]
[tex]\boxed{\begin{array}{l}\rm 2)\\\sf A=\dfrac{8^2\sqrt{3}}{4}\\\\\sf A=\dfrac{\diagdown\!\!\!\!\!\!6\!4\sqrt{3}}{\diagdown\!\!\!\!\!\!4}\\\\\sf A=16\sqrt{3}~cm^2\end{array}}[/tex]
[tex]\boxed{\begin{array}{l}\rm 3)\\\sf A=\dfrac{(34+10)\cdot\diagdown\!\!\!\!\!\!1\!6}{\diagdown\!\!\!\!\!\!2}\\\\\sf A=44\cdot8\\\sf A=352~m^2\end{array}}[/tex]
