解：?$(1)$?∵?$∠C=90°，$??$∠A=60°$?
∴?$∠B=90°-∠A=30°$?
∴?$b=\frac {1}{2}\ \mathrm {c}=\frac {1}{2} ×8 \sqrt{3}=4 \sqrt{3}，$??$a=c · s in 60°=8 \sqrt{3} × \frac {\sqrt{3}}{2}=12$?
∴?$∠B=30°，$??$a=12，$??$b=4 \sqrt{3} $?
?$(2)$?∵?$∠C=90°，$??$∠A=45°$?
∴?$∠B=90°-∠A=45°$?
∴?$a=b=3 \sqrt{6}，$??$c=\frac {a}{sin 45°} =\frac {a}{\sqrt{2}2} =\sqrt{2}\ \mathrm {a}=\sqrt{2} ×3 \sqrt{6}=6 \sqrt{3}$?
∴?$∠B=45°，$
??$b=3 \sqrt{6}，$
??$c=6 \sqrt{3}$
