2sin²（x／2)＋5sin(x/2)－3＝0
[2sin(x/2)-1][sin(x/2)+3]=0
sin(x/2)=-3舍去
所以sin(x/2)=1/2
x/2=2kπ+π/6,x/2=2kπ+5π/6
x=4kπ+π/3,x=4kπ+5π/3