(i) If the slope of the line is zero it means

M = tan θ

M = tan 0

Since, m = 0

So, The line is parallel to x - axis .

(ii) If the slope of the line is positive it means

Since θ is an acute

So, The line makes an acute angle with the positive x - axis .

(iii) If the slope of the line is positive it means

Since, θ is an obtuse

So, The line makes an obtuse angle with positive x - axis .