1)f(x)=f(-x)偶函数
2)x=700π时,-(2/3)^|x|<0,(sinx)^2=0,f(x)<1/2
3)如果学过极限
x=kπ+π/2时,
lim(k→∞)(2/3)^x=0,随着k无穷大,-(2/3)^|x|无限接近0
1≥(sinx)^2≥0
f(x)最大值1+1/2=3/2
4)
|x|≥0
(2/3)^|x|≤1, -(2/3)^|x|≥-1
(sinx)^2≥0
x=0时,f(x)最小值-1/2
如果没有学过极限,直接选4)