cos2x=1-2sin^2x证明

①原式=f(x)=2cos2x+sinx^2=2cos2x+1-cos2x/2=3/2cos2x+1/2故f(π/3)=3/2*cos2π/3+1/2=-3/4+1/2=-1/4②依f(x)=3/2c

y=2(1-2sin²x)+sin²x-4cosx=2-3sin²x-4cosx=2+3cos²-3-4cosx=3cos²-4cosx-1;再问：-

诱导公式f(x)=(1+2cos²x-1)/(4cosx)+asin(x/2)cos(x/2)=(cosx)/2+a/2*sinx=(a/2)sinx+(1/2)cosx=√[(a/2)&s

f(x)=(√3/2)sin2x+(1/2)cos2x+(√3/2)sin2x-(1/2)cos2x+cos2x+1=√3sin2x+cos2x+1=2sin(2x+π/6)+1周期T=2π/2=π对

(sinx)^2表示sinx的平方(sinx)^2+2(sinx)^2cosx+(cosx)^2-(sinx)^2=12(sinx)^2cosx+(cosx)^2=(sinx)^2+(cosx)^22

函数f(x)=2sin^2(x+π/4)-√3cos2x-1=-cos(2x+π/2)-√3cos2x=sin2x-√3cos2x=2sin(2x-π/3)1.当x属于R时,函数f(x)的最小正周期T

(1+cos2x)²-2cos2x-1=1+2cos(2x)+cos²(2x)-2cos(2x)-1=cos²(2x)=[cos²(x)-sin²(x

看图片吧

F(X)=(1+cos2x)sin²x问F(X)是最小正周期为多少的什么函数F(x)=(1+cos2x)sin²x=(1+cos2x)(1-cos2x)/2=(1-cos²

2cos2x+sin^2x=2(cos^2x-sin^2x)+sin^2x=2cos^2x-sin^2x=3cos^2x-1

cosx+cos2x+...+cosnx=1/2[(cosx+cosnx)+(cos2x+cos(n-1)x)+...+(cosnx+cosx)]=[cos(n+1)x/2][cos((n-1)x/2

即cos^8x-sin^8x=(cos^4x+sin^4x)(cos^4x-sin^4x)=(cos^4x+sin^4x)(cos²x+sin²x)(cos²x-sin&

两边求平方得：sin(x/2)^2+cos(x/2)^2+2sin(x/2)cos(x/2)=1/4-->1+sin(x)=1/4-->sin(x)=-3/4cos(2x)=1-2sin(x)^2=1

f(x)=sin2x*(根3/2)+cos2x*(1/2)+cos2x+1=根3/2*sin2x+3/2cos2x+1=根3（1/2*sin2x+根3/2*cos2x)+1=根3*sin(2x+pi/

f(x)=((1+cos2x)^2-2cos2x-1)/(sin(π/4+x)sin(π/4-x))=(cos2x)^2/((sinπ/4cosx+cosπ/4sinx)(sinπ/4cosx-cos

sin(x/2)的周期是4pi,cos2x的周期是pi,sin(x/2)+cos2x的周期是其最小公倍数,自然是4pi

f(sinx-1)=cos2x+2cos2x=1-2sin^2xf(sinx-1)=3-2sin^2x=-2(sinx-3/4)^2+7.5f(x)=-2(x+1/4)^2+7.5

f(x)=(1+cos2x+8sin^2x)/sin2xf(x)=(1+2cosx²-1+8sin²x)/2sinxcosxf(x)=(cosx²+4sin²x

sin2x+sin(π-x)/2cos2x+2sin^2x+cos(-x)=sin2x+sin(x)/2cos2x+2sin^2x+cos(x)=(2cosxsinx+sinx)/2cos²