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phatthemkem

a) $tgB=\frac{AC}{AB}=\frac{8}{15}$\Leftrightarrow $AC=\frac{8AB}{15}=\frac{8.30}{15}=16 cm$

\Rightarrow $BC=\sqrt{AB^2+AC^2}=\sqrt{30^2+16^2}=34 cm$

b) $sinB=\frac{AC}{BC}=\frac{16}{34}=\frac{8}{17}$

$cosB=\frac{AB}{BC}=\frac{30}{34}=\frac{15}{17}$

$cotB=\frac{AB}{AC}=\frac{30}{16}=\frac{15}{8}$

c) $sinC=\frac{AB}{BC}=\frac{30}{34}=\frac{15}{17}$

$cosC=\frac{AC}{BC}=\frac{16}{34}=\frac{8}{17}$

$tgC=\frac{AB}{AC}=\frac{30}{16}=\frac{15}{8}$

$cotC=\frac{AC}{AB}=\frac{16}{30}=\frac{8}{15}$
 
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