sin∧4α+cos∧4α=(sin^2a+cos^2a)-2sin^2acos^2a=1-2sin^2acos^2asinα-cosα=m,(sinα-cosα)^2=m^22sinacosa=1-m^2sin^2acos^2a=(1-m^2)/4sin∧4α+cos∧4α=1-2sin^2acos^2a=1-(1-m^2)/2=(1+m^2)/2