The slope of x -axis is zero and the slope of y -axis is not defined. HOW AND WHY ??
The said line in our study material is:
slope of x-axis is zero and the slope of y-axis is not defined.
Here, we are talking about the slope of both the axis with respect to horizontal.
In case of x-axis, θ = 0° and in case of y -axis, θ = 90°.
So, slope of x -axis = tan θ = tan 0° = 0
Similarly, slope of y -axis = tan θ = tan 90° and we know that value of tan 90° is undefined.
So, this is the only reason why slope of y-axis is undefined.
Hope you get it!!