Question

A straight line, makes an angle of ${60}^{\circ }$ with each of y and z-axis,then the inclination of the line with x-axis is

• A. ${60}^{\circ }$
• B. ${30}^{\circ }$
• C. ${45}^{\circ }$
• D. ${75}^{\circ }$

Answer 1

The correct option is C ${45}^{\circ }$

If $\alpha$ is a single at which the straight line is inclined to x-axis, then $co{s}^2\alpha +co{s}^2{60}^{\circ }+co{s}^2{60}^{\circ }=1$
$\Rightarrow co{s}^2\alpha =\frac{1}{2}$
$\Rightarrow \alpha ={45}^{\circ }or{135}^{\circ }$.