Piston displacement

[Flimjabs]

Hi everybody
so I had a series of questions about a piston
Displacment =25cos(200t+1.3)
I'm stuck on part E which is
Where does the piston sit when t=0
I have attached the making to this thread, can someone check my reworking, I'm assuming I need to convert radians to degrees so
25cos(1.3×57.3)=6.68mm is this the position when t=0 or do I subtract that from 25mm?
Thank you in advance

 

[HallsofIvy]

What is the relationship between "where the piston sits" and "the displacement"? I don't know why you would "have to convert radians to degrees". How are you calculating the cosine? I would assume you are using a calculator but every calculator I have seen will accept and angle in radians as well as degrees.