Find the slope and inclination angle of the straight line passing through points a (3.5) and B (A.2)

Find the slope and inclination angle of the straight line passing through points a (3.5) and B (A.2)

Classification discussion:
(1) When a = 3
The straight line is x = 3
The slope does not exist and the tilt angle is 90 degrees
(2) When a ≠ 3
The slope is k = (2-5) / (A-3) = - 3 / (A-3)
The tilt angle is θ = arctank = arctan [- 3 / (A-3)] [the range is 0 ≤ θ < π]
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