Write the value of if the normal to the curve y = f(x) at (x, y) is parallel to y-axis.
Given that the normal to the curve y = f(x) at (x, y) is parallel to y-axis.
We know that the slope of the y-axis is ∞.
∵ Slope of the normal = Slope of the y-axis = ∞
∴ Slope of the tangent