How do you find a vertical asymptote for y = sec(x)?

1 Answer
Sep 25, 2014

The vertical asymptotes of y=secx are

x={(2n+1)pi}/2, where n is any integer,

which look like this (in red).

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Let us look at some details.

y=secx=1/{cosx}

In order to have a vertical asymptote, the (one-sided) limit has to go to either infty or -infty, which happens when the denominator becomes zero there.

So, by solving

cosx=0

Rightarrow x=pm pi/2, pm{3pi}/2, pm{5pi}/2, ...

Rightarrow x=pi/2+npi={(2n+1)pi}/2, where n is any integer.

Hence, the vertical asymptotes are

x={(2n+1)pi}/2, where n is any integer.