We are given the following function
[tex]\pi\sin (\pi t-\pi)+\pi[/tex]
Recall that the sine functions looks something like this
In our example, we have drawn a sine function that has as midline the line y=1. Note that the midline is a horizontal around which the function sine oscilates. In general, the sine function looks like this
[tex]y=A\cdot\sin (Bt-C)+D[/tex]
where A,B,C and D are numbers. In this case, number D indicates the midline. So, the midline would be given by the line y=D.
From our function, we can see that
[tex]D=\pi[/tex]
Thus, the line y=pi is a midline of the given sine function.
