S=(cos^2 x+cos^4 x+.+cos^2n x)+(sin^2x+sin^4 x+.+sin^2n x)数列求和题!答案是(cos^4 x+sin^4 x-cos^2n+4 x-sin^2n+4 x)/sin^2 x.cos^2 x
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S=(cos^2 x+cos^4 x+.+cos^2n x)+(sin^2x+sin^4 x+.+sin^2n x)数列求和题!答案是(cos^4 x+sin^4 x-cos^2n+4 x-sin^2n+4 x)/sin^2 x.cos^2 x
S=(cos^2 x+cos^4 x+.+cos^2n x)+(sin^2x+sin^4 x+.+sin^2n x)数列求和题!
答案是(cos^4 x+sin^4 x-cos^2n+4 x-sin^2n+4 x)/sin^2 x.cos^2 x
S=(cos^2 x+cos^4 x+.+cos^2n x)+(sin^2x+sin^4 x+.+sin^2n x)数列求和题!答案是(cos^4 x+sin^4 x-cos^2n+4 x-sin^2n+4 x)/sin^2 x.cos^2 x
提示:两个等比数列和,再求和.
S=(cos²x)[1-(cos²x)ⁿ]/(1-cos²x) +(sin²x)[1-(sin²x)ⁿ]/(1-sin²x)
=(cos²x)[1-(cos²x)ⁿ]/sin²x +(sin²x)[1-(sin²x)ⁿ]/cos²x
=[(cos⁴x)-(cosx)^(2n+4)+(sin⁴x)-(sinx)^(2n+4)]/(sin²xcos²x)
证明cos 2x cos x=1/2(cos x+cos 3x)
S=(cos^2 x+cos^4 x+.+cos^2n x)+(sin^2x+sin^4 x+.+sin^2n x)数列求和题!答案是(cos^4 x+sin^4 x-cos^2n+4 x-sin^2n+4 x)/sin^2 x.cos^2 x
求解三角函数 cos 2 X (1 - 2 sin ^2 2 X) + cos 4 X ( 1 + cos 2 X)cos 2 X (1 - 2 sin ^2 2 X) + cos 4 X ( 1 + cos 2 X) = cos 2 X cos4X (1 + cos 2 X) = cos 4 X (1 +2cos 2X) = 0
y=2cos x (sin x+cos x)
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cos 2x(1-2sin^2 2x) + cos 4x (1+cos 2x)=
证明sin^4x-cos^4x=sin^2x-cos^2x
求证sin^4x-cos^4x=sin^2x-cos^2x
证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4
关于三角函数的一道题(高中)cos(10)*cos(20)*cos(40)=?类似cos(X)*cos(2x)*cos(4x)=?sin(x)*sin(2x)*sin(4x)=?的题目有没有什么规律
2(cos x)^2=1+cos 2x,
2cos^2x等于cos^4x么?
sin^2 x-cos^2 x=cos
cos(x-2派/3)=-cos(x+派/3)
y=(cos x-2)/(cos x-1)的值域
设函数f(x)=a*b,其中向量a=(2cos x,1),b=(cos x,根号3 sin 2x),x属于(-30,30度),f(s)=3/4,求cos(2x)
Cos x=-1/2
y=cos^2 x-cos x +1的值域y=cos^2 x+cos x +1的值域,