sinα=1/2(|x|+1/|x|),则α的值为?A、2kπ,k属于z B、kπ,k属于z c、（2k+1）π,k属于z D、2kπ+π/2,k属于z

傅里叶级数作图f（x）=2sin[x] - sin[2x] + 2/3sin[3x] - 1/2sin[4x]我用mathematica输入程序Plot[{2sin[x],-2sin[x],2sin[x] - sin[2x],-2sin[x] + sin[2x],2sin[x] - sin[2x] + 2/3sin[3x],-2sin[x] + sin[2x] - 2/3sin[3x],2sin[x] - sin[2x] + 2/3si 求证:(sin 2x /(1-cos 2x) )·(sin x /(1+sin x))=tan (π/4-x/2). 求证（cos^2 x-sin^2 x)(cos^4 x+sin^4 x)+1/4 sin 2x sin 4x=cos 2x sin(sinx)/x,x 趋于0的极限sin(sin(x))/x=[sin(sin(x))/sin(x)]*sin(x)/x=1*1=1sin(sin(x))/sin(x)这一部我不明白阿 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)] s = 2*sin(x)-sin(2*x)+2/3*sin(3*x)-1/2*sin(4*x)+2/5*sin(5*x)用matlab画图,求教啊 求极限 （（sin(x^3+x^2-x)+sin x) /x x→0 已知lim sinx/x=1 (sin 1/x) /x 化简(sin x+cos x-1)(sin x-cos x+1)/sin 2x 怎么证明2(1-sin x)(1+cos x)=(1-sin x+cos x)^2 2ln|sec X+tan X|=ln|(1+sin x)/(sin x-1)|怎么证 x*（1+sin^2 x )/sin^2x 不定积分 求证：(sin x+cos x)(1-tan x)=(2sin x)/(tan2x) 求证：tan x/2=sin x/(1+cos x) 求证：1-sin(x)=cos(x)*tan(x/2) 已知函数f(x)=(1+1 anx)sin^2x+m sin(x+π/4)sin(x-π/4) 已知-π/2＜x＜0,sin x+cos x=1/5求sin 2x+2 sin f(x)=（1+cotx)sin^2x-2sin(x+π/4)sin(x-π/4)还有一题,