f(x)在R上为偶函数，f(x＋1）＝－f(x)f(x+2)=f(x)所以f(x)是以2为周期的函数。所以f(3)=f(-1)f(2)=f(0)f(√2）=f(√2-2) √2≈1.4因为f(x)在区间【-1，0】上为递增所以f(3)
