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ǰλãҳ >> ΪʲôCos2x=1%2(sinx)^2 >>

ΪʲôCos2x=1%2(sinx)^2

cos2x=(cosx)^2-(sinx)^2 =1-(sinx)^2-(sinx)^2 =1-2(sinx)^2

⣺ cos2x=cos(x+x) =cosx*cosx-sinx*sinx =(cosx)^2-(sinx)^2 ʽӦõcos(x+y)=cosx*cosy-sinx*sinyx=y

cos2x=cos^2x-sin^2x=1-2sin^2x=2cos^2x-1 μ

cos2x=cos(x+x) cosx^2-sinx^2=cos2x +1 cosx^2+1-sinx^2=cos2x 2cosx^2=1+cos2x cosx^2=(1+cos2x)/2

ҵĺͽǹʽɵãcos2x=cos(x+x)=(cosx)^2-(sinx)^2 (cosx)^2=1-(sinx)^2 ԣcos2x=1-(sinx)^2-(sinx)^2=1-2(sinx)^2

ʵe^x1ȼxln(1+x)ȼxsinxȼx1(1+sinx)^x1e^(xln(1+sinx))1ȼxln(1+sinx)ȼxsinxȼx^22ش﷨(tanx)^xlim(tanx)^x=e^(limxlntanx)=e^(limlntanx/(1/x))e^(limsec^2x/tanx/(...

## ̩չʽ ˼·ȫȷӦsinx̩չˣοͼ

sin2xdx=0.5sin2xd2x=-0.5cos2x+C d(sinx)^2=2sinxdsinx=2sinxcosxdx=sin2xdx !ͳڻֳϣC=0.5: 0.5-0.5cos2x=0.5(1-cos2x)=(sinx)^2 һ! ʵ: sin2xdx=2sinxcosxdx=sinxdsinx=(sinx)^2+C C=0 ...

-1/4(cos2x)=-1/4(1-2sin^2x)=1/2(sinx)^2-1/4 -1/4(cos2x)1/2(sinx)^2ֻһ һ󣬼sinxcosxdx=-1/4(cos2x)+C صڣһĻΪǸCDzȷģ-1/4(cos2x)1/2(sinx)^2...

f(sinx)=1+cos2x = 1+ (1-2(sinx)^2) = 2 - 2(sinx)^2 f(x) =2-2x^2 lim(x-> )(3x^3-7x+4)/(7x^3-8x+9) =lim(x-> )(3-7/x+4/x^3)/(7-8/x^2+9/x^3) =3/7

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