trouble interpreting a problem

express each trigonometric function as a corresponding function of an angle in the first quadrant (0<= Theata <= PIE/2) preceded by a + or - sign:

a)sin 9pie/2

b)sin 7pie

c)sin(-7pie/3)

theres i # of problems, but only posting up to c.

I figure like x is an angle, so f(x) is the function. so they want me to express a trig function as a function of an angle... but isnt a trig function already a function of an angle? and what do they mean preceded by a + or - sign, does that mean f(-x) ? yeah I dont get what they want me to do.