y=sin(-3x+四分之兀〕=sin(3x+3兀/4〕 增函数区间 2π-π/2<=3x+3兀/4<=2π+π/2 2kπ-5π/4<=3x<=2kπ-π/2 即增函数区间 2/3kπ-5π/12<=x<=2/3kπ-π/6
