Asked by Amy McMahon

The **curve y = f(x)** has a vertical tangent line at the point (a, f(a)) if (i) f(x) is a continuous at x = a. of f(x), the limit should be an appropriate side limit. See Example 1). When both (i) and (ii) are satisfied, the vertical line x = a is a tangent line of the curve y = f(x) at the point (a, f(a)).

Rosa Pérez, BA Contributor