∵f(x)是定义在R上的奇函数
∴f(0)=0
又：f(x+1)=-f(x)
令x=x+1,则f(x+2)=-f(x+1) = f(x)
∴f(2011) = f(2009) = f(2007)=.f(1) = f(-1) = f(0) = 0