- Chọn đáp án: A. $\frac{1}{\sqrt{3}}$.
N đối xứng với M qua trục tung ta có:
$x_{N} = - x_{M}$
$\Rightarrow cos\widehat{xON} = -cos\widehat{xOM}$
$\Rightarrow cos\widehat{xON} = 150^{o} = -(\frac{\sqrt{3}}{2}) = \frac{\sqrt{3}}{2}$
$y_{N} = y_{M}$
$\Rightarrow sin\widehat{xON} = sin\widehat{xOM}$
$\Rightarrow sin\widehat{xON} = 150^{o} = \frac{1}{2}$
$tan\widehat{xON} = \frac{sin\widehat{xON}}{cos\widehat{xON}} = \frac{1}{\sqrt{3}}$