# How do you find the amplitude and period of y = 2 cos (pi x + 4pi) ?

Sep 10, 2015

Amplitude: <-2;2>

Period: $2$

#### Explanation:

If you have a trigonometric function like: $f \left(x\right) = a \cos \left(b x + c\right)$, then to calculate amplitude ($A$) and period ($P$) you can use:

A=<-a;a>

$P = \frac{2 \pi}{b}$

If the function was $\tan$ or $c t g$ then in period you would have to use

$P = \frac{\pi}{a}$ instead of $P = \frac{2 \pi}{a}$