f(x)= 5cos(x) +3
1) Considering a generic cosine function as y= Acos(Bx +C) +D the amplitude, or half the length between the highest point of the curve is found by:
[tex]Amplitude\colon\text{ |A|}[/tex]2) Examining the given options, then we can state that f(x)= 5cos(x) +3 has an amplitude of 5 units