Question

For the function given, state the middle line; f(t) = 40cos (80t + 20)

Answer 1

In the standard form of the equation

$\\ \ f(t)=Acos[b(t\pm c)]+k$

The middle line =k

For our given problem

f(t) = 40cos (80t + 20)

On comparison we get k=0

Hence middle line=0