The Straight Lines — MATHS STD 11 Science — Question

1. If the slope $=\tan\theta=0\Rightarrow\theta=0$

When the slope of line is zero then the line is parallel to x axis.

2. If the slope is positive then $\tan\theta=$ positive $\Rightarrow\theta=$ acute

Thus the line makes an acute angle $\Big(0<\theta<\frac{\pi}{2}\Big)$ with the positive $\text{x}$ axis.

3. When the slope is negative then $\tan\theta=$ negative $\Rightarrow\theta$ is obtuse

Thus the line makes an abtuse angle $\Big(\theta<\frac{\pi}{2}\Big)$with the positive x axis.