1. The problem is to express $Z$ as a function of $\cos$. 2. Usually, $\cos$ is followed by a variable or expression, for example, $\cos x$, which denotes the cosine of $x$. 3. Assuming the expression is $Z = 1 + \cos x$, this means $Z$ is the sum of 1 plus the cosine of $x$. 4. The function can be written as $$Z = 1 + \cos x$$ 5. This represents a trigonometric function where the graph oscillates between 0 and 2 because the range of $\cos x$ is $[-1,1]$. 6. So, $Z$ will range from $1-1=0$ to $1+1=2$. 7. The function is useful in contexts where a phase shift by 1 is needed on the cosine wave.