fx=sinpaix/3-genhao3cospaix/3=2sin(pai(x-1)/3)
so fx=f(x+6)
f1+f2+f3+f4+f5+f6=0
原式=（f1+...f6）+(f7+...f12)+.+F(2011)+f2012=0+.0+ 0+2xgenaho3/2=genaho3