When it asks for f(-π) or f(0) or f(whatever) it essentially means you need to sub in the values for whatever into the bracket into the function
so if [tex]f( \theta) =sin(\theta) [/tex]
and then you're asked to find f(-π) then it essentially wants you to find sin(-π)
Therefore
f(-π) = sin(-π) = 0
f(0) = sin (0) = 0
f(π) = sin(π) = 0
f(2π) = sin2π = 0
