∵ sinα,cosα 是方程3x²-mx+1=0的两根∴ sinα+cosα =m/3； sinα*cosα = 1/3；∴ (sinα)^4 + (cosα)^4 = (sinα + cosα)² -2(sinαcosα)²=1 - 2*(1/3)² =7/9