Question

Find the equation of a line parallel to X-axis and passing through the origin.

Answer 1

Let A be a point on X-axis.
The x-axis makes: an angle of $0^{\circ }$ with x-axis itself.
an angle of ${90}^{\circ }$ with y-axis and
An angle of ${90}^{\circ }$ with z-axis.
Direction ratios of x-axis are $(\cos 0,\cos 90,\cos 90)=(1,0,0)$
Since, the line passes through the origin $(0,0,0$).
Therefore, the equation of OA is given by, $\frac{x-0}{1}=\frac{y-0}{0}=\frac{z-0}{0}\Rightarrow \frac{x}{1}=\frac{y}{0}=\frac{z}{0}$