Aplicand teorema sinusurilor, conform figurii : [tex] \frac{AB}{sinADB}= \frac{BD}{sin60},deci,\frac{8}{sinADB}= \frac{8 \sqrt{3} }{ \frac{ \sqrt{3} }{2} },deci,sinADB= \frac{1}{2}, [/tex], deci masura ∡ ADB=30°, deci masura lui ∡ABD=90°, adica DB=inaltime, de unde ariua A=8*8√3=64√3 cm².