Question

Can someone explain to me how to get this correct?

Answer 1

do you know what the plot of a "normal" sin(x) looks like ?

Answer 2

actually no I dont

Answer 3

I think they expect you to know
see https://en.wikipedia.org/wiki/Sine
what is the "middle line" (I assume the line the sin seems to wiggle above and below)
in their graph?

Answer 4

alright let me see

Answer 5

@phi that would mean zero though?

Answer 6

yes, the zero is what the sin wanders around. I think that is what they mean by the middle line.

the "middle line" is y=0
if you add pi to it, as in your problem, everything is shifted up by pi
the middle line becomes y= 0+pi or just y= pi