Question

What can be said regarding a line if its slope is

(i) zero (ii) positive (iii) negative ?

Answer 1

$\text{(i) If slope}=tan\theta =0\Rightarrow \theta =0\text{When the slope of a line is zero then the line is parallel to x-axis.}\text{(ii) If the slope is positive then}tan\theta =positive\Rightarrow \theta =acute\text{Thus the line makes an acute angle}(0<\theta <\frac{\pi }{2})\text{with the positive x-axis}\text{(iii) When the slope is negative then}tan\theta =negative\Rightarrow \theta \text{is obtuse}\text{Thus the line makes an obtuse angle}(\theta >\frac{\pi }{2})\text{with the positive x-axis.}$