Question

The angle which a vector $\hat{i}-\hat{j}+\sqrt{2}\hat{k}$ makes with y - axis is

• A. ${60}^{\circ }$
• B. ${120}^{\circ }$
• C. ${150}^{\circ }$
• D. $ta{n}^{-1}(-\frac{1}{2})$

Answer 1

The correct option is B ${120}^{\circ }$

Assume that the angle made by vector with y-axis is $\beta$,
$\cos \beta =\frac{A_y}{A}=\frac{-1}{\sqrt{(1{)}^2+(-1{)}^2+(\sqrt{2}}{)}^2}$
$\cos \beta =-\frac{1}{2}$
$\beta ={120}^{\circ }$