We know that the slope of a given line is given by

Slope = Where angle of inclination

(i) Given that θ = 30°

Slope = tan(30°) =

(ii) Given that θ = 120°

Slope = tan(120°) = tan(90°+30°) = -cot(30°) =

(iii) Given that θ = 135°

Slope = tan(135°) = tan(90°+45°) = -cot(45°)

(iv) Given that θ = 90°

Slope = tan(90°) = ∞