a) $\widehat{B}$ = $90^{\circ}$ - $\widehat{C}$ = $90^{\circ}$ - $30^{\circ}$ = $60^{\circ}$
sinB = $\frac{CA}{CB}$ $\Rightarrow $ CB = $\frac{16}{\sqrt{3}}$ cm
$\Rightarrow $ AB = $\frac{8}{\sqrt{3}}$ cm
b) $\widehat{B}$ = $90^{\circ}$ - $\widehat{C}$ = $90^{\circ}$ - $45^{\circ}$ = $45^{\circ}$
$\Rightarrow $ AC = AB = 12 cm
sinC = $\frac{AB}{CB}$ $\Rightarrow $ CB = 12$\sqrt{2}$ cm
c) $\widehat{C}$ = $90^{\circ}$ - $\widehat{B}$ = $90^{\circ}$ - $35^{\circ}$ = $55^{\circ}$
sinB = $\frac{AC}{CB}$ $\Rightarrow $ AC = 5,7 cm
$\Rightarrow $ AB = 8,19 cm
d) BC = $\sqrt{AB^{2} + AC^{2}}$ = $\sqrt{10^{2} + 24^{2}}$ = 26 cm
sin B = $\frac{AC}{CB}$ = $\frac{24}{26}$ = $\frac{12}{13}$
$\Rightarrow $ $\widehat{B}$ = $67,38^{\circ}$
$\widehat{B}$ = $90^{\circ}$ - $\widehat{C}$ = $90^{\circ}$ - $67,38^{\circ}$ = $22,62^{\circ}$.
Bình luận