[tex]\displaystyle\\
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Enuntul nu spune care laturi ale triunghiului isoscel ABC sunt egale, dar faptul ca unghiul A este obtuz inseamna ca AB = AC.
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\text{In }\Delta ABC \text{ avem:}\\
\sphericalangle A = 150^o\\
AB = AC = 36~cm\\\\
\text{Calculam aria cu formula: } \boxed{A_{_{\Delta ABC}} = \frac{bc\,\sin A}{2}}
[/tex]
[tex]\displaystyle\\
A_{_{\Delta ABC}} = \frac{AB\times AC\,\sin 150^o}{2} =\\\\
= \frac{AB\times AC\,\sin (180^o-30)}{2} = \\\\
= \frac{AB\times AC\,\sin (30)}{2} =\\\\
= \frac{36\times 36\times \dfrac{1}{2} }{2} =\frac{36\times 36}{4} =36\times 9 =\boxed{\bf 324~cm^2}[/tex]
