求证!cos^8x-sin^8x+1/4sin2xsin4x =cos2x求数学大神帮忙详细过程 谢谢

求证 cos^8(x)-sin^8(x)=cos2x【1-1/2sin^2（2x)】 求证!cos^8x-sin^8x+1/4sin2xsin4x =cos2x 求证（cos^2 x-sin^2 x)(cos^4 x+sin^4 x)+1/4 sin 2x sin 4x=cos 2x 求证(3-sin^4 x-cos^4 x)/2cos^2 x=1+tan^2 x+sin^2 x 求证:(sin 2x /(1-cos 2x) )·(sin x /(1+sin x))=tan (π/4-x/2). 求证：cos^8(x) - sin^8(x) + (1/4)sin2xsin4x = cos2x注：开头的cos、sin上的8是8次方,x不是在8上的,是在cos、sin上的 求证sin^4x+cos^4x=1-2sin^2xcos^2x 求证 sinˇ4X+sin²Xcos²X+cos²X = 1 证明一个sin&cos的等式证明 1+sin^2(x)+sin^4(x)+sin^6(x)=[1-sin^8(x)]/[cos^2(x)] 求证（cos^2x-sin^2x)(cos^4x+sin^4x）+1/4sin2xsin4x=cos2x 求证：1-cos^4x-sin^4x/1-cos^6x-sin^6x=2/3 求证sin^4x-cos^4x=sin^2x-cos^2x 求证!cos^8x-sin^8x+1/4sin2xsin4x =cos2x求数学大神帮忙详细过程 谢谢 求证：tan x/2=sin x/(1+cos x) 求证：1-sin(x)=cos(x)*tan(x/2) 三角等式求证：cos^6x+sin^6x=1-3sin^2x+3sin^4x 求证:cos^8x-sin^8x-cos2x = 1/8(cos6x - cos2x)还有，csc^4a(1-cos^4a)-2cot^2a d/dx sin^8(cos(4x))