w>0,∵x∈[-π/3,π/4],∴wx∈[-wπ/3,wπ/4],
[-wπ/3,wπ/4]包含0,而原点附近的增区间是[-π/2,π/2],
-wπ/3≥-π/2,且wπ/4≤π/2,解得0