pt $\Leftrightarrow -2\sin ^{2}x+3\sin x-2m+2=0 (1)$đặt $t=\sin x , t\in \left ( 0;1 \right )$ , pt tt
$-2t^{2}+3t-2m+2=0$ (2)
pt có 4 no $\in \left ( 0;\Pi \right ) \Leftrightarrow (2) $ có 2 no pb $\in \left ( 0;1 \right )$
$\Leftrightarrow m\in \left ( \frac{3}{2};\frac{25}{16} \right )$