Question

Giải tam giác ABC vuông tại A, biết rằng :

a) \(b=10cm,\widehat{C}=30^0\)

b) \(c=10cm,\widehat{C}=45^0\)

c) \(a=20cm,\widehat{B}=35^0\)

d) \(c=21cm,b=18cm\)

Answer 1

a) (H.a)

$\hat{B}={90}^{\circ }-{30}^{\circ }={60}^{\circ }.$

$AB=AC\cdot tgC=10\cdot tg{30}^{\circ }\approx 5,774\left(cm\right)$

$BC=\frac{AC}{cosC}=\frac{10}{\cos {30}^{\circ }}\approx 11,547\left(cm\right)$.

b) (H.b)

$\hat{B}={90}^{\circ }-{45}^{\circ }={45}^{\circ }.$

$\Rightarrow AC=AB=10\left(cm\right);$

$BC=\frac{AB}{sinC}=\frac{10}{\sin {45}^{\circ }}\approx 14,142\left(cm\right)$

c) (H.c)

$\hat{C}={90}^{\circ }-{35}^{}$