1.证明:sin^4α－cos^4α=(sin^2α－cos^2α)*(sin^2α+cos^2α)=(sin^2α－cos^2α)*1=sin^2α－cos^2α2.证明:sin^4α+sin^2αcos^2α+cos^2α=(sin^2a)^2+sin^2αcos^2α+cos^2α=sin^2a*(sin^2a+cos^2a)+cos^2a=...