令 u=sin x,v=cos x,则 u +v =m,①u^2 +v^2 =1.② 由 ①^2 -② 得2uv =m^2 -1,即 uv =(m^2 -1)/2.③由 ②③ 得u^4 +v^4 =(u^2 +v^2)^2 -2 (uv)^2=1 -(1/2) (m^2 -1)^2= (1+2 m^2 -m^4) /2.即 (sin x)^4 +(cos x)^4 =...