How to find a vertical asymptote

Step-by-step explanation:

Generally's rational functions that have vertical asymptotes, even trig functions (which, like the tangent function, are often rational).

If the given function is the ratio of two functions, polynomial or otherwise, the graph of the given function has an asymptote at any x value for which the denominator is zero. Example: y = tan x = (sin x) / (cos x) has vertical asysmptotes at π/2, 3π/2, and so on, because the denominator cos x is zero for those angles.