Question 1138152
<br>
{{{y = a*cos(b(x-c))+d}}}<br>
a is the amplitude
b determines the period: b = 2pi/period
c is the phase (horizontal) shift
d is the vertical shift<br>
The given equation, in that form, is<br>
{{{y = 3*cos((pi/4)(x-2))-1}}}<br>
The period is determined by b; b = 2pi/period.  Since b = pi/4, the period is<br>
{{{2pi/(pi/4)}}} = 8