Solution: (1). When x is the angle of the first quadrant (including x=2kπ and x=2kπ+π/2):

y =(sinx/sinx)+(cosx/cosx)+(tanx/tanx)+(cotx/cotx)= 1+ 1+ 1+ 1+ 1 = 4；

(2)。 When x is the angle of the second quadrant (including x=2kπ+π/2 and x=2kπ+π):

y =(sinx/sinx)+(-cosx/cosx)+[tanx/(-tanx)]+[(-cotx)/(cotx)]= 1- 1- 1- 1 =-2；

(3)。 When x is the angle of the third quadrant (including x=2kπ+π and x=2kπ+3π/2):

y =[sinx/(-sinx)]+(-cosx/cosx)+(tanx/tanx)+(cotx/costx)=- 1- 1+ 1+ 1 = 0；

(4)。 When x is the fourth pixel, the angle is (including x=2kπ+3π/3 and x=2kπ):

y =[sinx/(-sinx)]+(cosx/cosx)+[tanx/(-tanx)]+[(-cotx)/(cotx)]=- 1+ 1- 1- 1 =-2。

So the value range of function y is {-2, 0, 4}.