The angle at which the line, $\frac{x-1}{0}=\frac{2-y}{-1}=\frac{2z-3}{-2}$ is inclined with the positive direction of z-axis is |
$\frac{\pi}{4}$ $\frac{\pi}{2}$ $\frac{2\pi}{3}$ $\frac{3\pi}{4}$ |
$\frac{3\pi}{4}$ |
The correct answer is Option (4) → $\frac{3\pi}{4}$ Given line: $\frac{x-1}{0}=\frac{2-y}{-1}=\frac{2z-3}{-2}$ Direction ratios: $(0,-1,-2)$ Angle $\theta$ with positive z-axis is given by: $\cos\theta = \frac{\text{z-component}}{\text{magnitude of direction vector}}$ $\Rightarrow \cos\theta = \frac{-2}{\sqrt{0^2+(-1)^2+(-2)^2}}=\frac{-2}{\sqrt{5}}$ $\cos\theta$ is negative, so $\theta$ is an obtuse angle. $\theta = \pi - \cos^{-1}\left(\frac{2}{\sqrt{5}}\right)$ Approximation gives $\theta=\frac{3\pi}{4}$ $\theta=\frac{3\pi}{4}$ |