Đáp án:
Giải thích các bước giải:
$\cos(C)$ = $\dfrac{1}{3}$
$\Leftrightarrow$ $\dfrac{CB}{AC}$ = $\dfrac{1}{3}$
$\Leftrightarrow$ $\dfrac{5}{AC}$ = $\dfrac{1}{3}$
$\Leftrightarrow$ AC = 15 cm
Xét $\triangle$ ABC vuông tại B :
`AB^2` + `BC^2` = `AC^2`
$\Leftrightarrow$ `AB^2` = `AC^2` - `BC^2`
$\Leftrightarrow$ `AB^2` = `15^2` - `5^2`
$\Leftrightarrow$ `AB^2` = 200
$\Leftrightarrow$ AB = 10$\sqrt{2}$
$\sin(A)$ = $\cos(C)$ = $\dfrac{1}{3}$
$\cos(A)$ = $\dfrac{AB}{AC}$ = $\dfrac{10\sqrt{2}}{15}$ = $\dfrac{2\sqrt{2}}{3}$
$\tan(A)$ = $\dfrac{BC}{AB}$ = $\dfrac{5}{10\sqrt{2}}$ = $\dfrac{\sqrt{2}}{4}$
$\cot(A)$ = $\dfrac{AB}{BC}$ = $\dfrac{10\sqrt{2}}{5}$ = 2$\sqrt{2}$
