Question 1138151
<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 amplitude is a, which is 3.