?$解：①在Rt△ABC中，$?
?$因?yàn)锳C=12，BC=16$?
?$所以AB=\sqrt{AC2+BC2}=20$?
?$所以tanA=\frac {BC}{AC}=\frac {16}{12}=\frac {4}{3}$?
?$tanB=\frac {AC}{BC}=\frac {12}{16}=\frac {3}{4}$?
?$②在Rt△ABC中，$?
?$因?yàn)锽C=8 ， AB=\sqrt{73}$?
?$所以AC=\sqrt{AB2-BC2}=3$?
?$所以tanA=\frac {BC}{AC}=\frac {8}{3}，tanB=\frac {AC}{BC}=\frac {3}{8}$
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