Answer:
Step-by-step explanation:
The easiest way to do this is to get the period correct first.
If the function f(x) = cos(B * x) then the period is
P = 2*pi/B In this case B = 5
P = 2* pi/5
The frequency is the reciprocal of the period
f = 1/p
f = 1/(2pi/5) Now all you do is turn 2p/5 upside down.
f = 5/2*pi <<<< Answer
I don't know how simple your marker considers this, but it is the answer.
