sin(π 4-x)=(cosx-sinx) √2

f(x_=(cosx+sinx)(cosx-sinx)=cos²x-sin²x=cos2x所以T=2π/2=πf(α/2)=cosα=1/3sin²α+cos²

cos-x自己画个坐标就一目了然了

1.f（x）=2cosx*sin(x+π/3)-√3sin^2x+sinx*cosx=2cosx*sin(x+π/3)-2sinx*[(√3/2)sinx-(1/2)cosx]=2cosx*sin(x

∵f(x)=2sin(π-x)cosx=2sinxcosx=sin2x1、最小正周期T=2π/2=π.2、∵-π/6≤x≤π/2∴-π/3≤2x≤π,∴-√3/2≤f(x)≤1,∴最大值1,最小值-√

sin(x-3π/4)=sin[π-(π/4-x)]=sin(π/4-x)=-sin(x-π/4)sin(x-3π/4)cos(x-π/4)=-sin(x-π/4)cos(x-π/4)=-sin(2x

f（x）=2cosx*sin（x+π/3)-√3sinx^2+sinx*cosx=2cosx*(sinxcosπ/3+cosxsinπ/3))-√3sinx^2+sinx*cosx=sinxcosx+

√2sin(x-π/4)=√2(sinxcosπ/4-cosxsinπ/4)=√2[(1/√2)sinx-(1/√2)cosx]=sinx-cosx

是(sinx+cosx)/(sinx-cosx)=2和[2cos(π-x)-3sin(π+x)]/[4cos(-x)+sin(2π-x)]吗?如果是的话：(sinx+cosx)/(sinx-cosx)

sinx+cosx=√2(cos45°sinx+sin45°cosx)=√2sin(x+45°)==√2sin(x+π/4)

当K为奇数时,sin(kπ+x)=-2cos(kπ+x)即-sinx=-2(-cosx),于是tanx=-2.当K为偶数时,sin(kπ+x)=-2cos(kπ+x)即sinx=-2(cosx),于是

这个简单：f(x)=2cosx(sinxcos(pi/3)+cosxsin(pi/3))-根号33sin^2x+sinx*cosx=2sinxcosx+根号3cos2x=2sin(x+pi/3)所以：

f(x)=|sinx+cosx|=|√2（√2/2*sinx+√2/2*cosx|=|√2（sinx*cosπ/4+cosx*sinπ/4）|=|√2sin(x+π/4)|.

(cosx)'=[sin(π/2-x)]‘=cos(π/2-x)*(π/2-x)'=sinx*(-1)=-sinx

f(x)=4sinx*sin^2（(π+2x）/4)+（cosx+sinx）（cosx-sinx）=4sinx*[1-cos(π/2+x)]/2+cos²x-sin²x=sinx(

1).cosx≠0.x≠kπ+π/2.k∈Z.∴f(x)的定义域为{x│x≠kπ+π/2.k∈Z}.2)α是第四象限的角,切tanα=-4/3.sinα=-4/5,cosα=3/5.sin2α=2si

(1)cosx≠0x≠Kπ+π/2K∈Z(2)由tanα=-4/3可知:sinα=4/5,cosα=-3/5得：sin2α=2sinα*cosα=-24/25cos2α=1-2(sinα)^2=-7/

要用这个公式,你用错了cos(π/2+a)=-sinasina=-cos(π/2+a)2sin(x-π/4）sin（x+π/4）=-2cos[π/2+(x-π&

和差化积公式.sin(x+y)=sinx*cosy+cosx*siny

f(x)=sinx+cosx=√2（√2/2sinx+√2/2sinxcosx）-------(提一个√2出来)=√2（sinxcosπ/4+cosxsinπ/4）-（把（√2/2分别变为cosπ/4

y=(sinx)^2-cosx=1-(cosx)^2-cosx=-(cosx+1/2)^2+5/4x∈(-π/4,π/4)cosx∈(√2/2,1)令cosx=1,得y=-1令cosx=√2/2,得y