# How do you write an equation of the cosine function with the given amplitude = 3, period = pi, phase shift = –3/4pi, vertical shift = –3?

$y = - 3 + 3 \cos \left(2 x - \frac{3}{4} \pi\right)$
$y = \pm$(vertical shift)$+$(Amplitude)$\times \cos \left(k x + \phi\right)$
Where $k = \frac{2 \pi}{p e r i o d}$
$\phi =$ initial phase