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ΪʲôCos2x=Cos^{2}A%sin^{2}A

Ǻ͵ҹʽ cos(a+x)=cosacosx-sinasinx a=x cos(x+x)=cos2x =cosxcosx-sinxsinx =(cosx)^2-(sinx)^2 cos(2x)=(cosx)^2-(sinx)^2

(0 /2)(a²cos²x+b²sin²x)dx =(0 /2)(a²cos²x+b²(1-cos²x)dx =(0 /2)(a²-b²)cos²x dx+(0 /2)b²dx =(0 /2)(a²-b²)(1+cos2x)/2 dx+(0 /2)b²dx =½...

ֻ㵽ˣòƲûгȱʽӦ󶨻

õĹʽ 2cos^2 x -1 =cos2x sin()sincos¡cossin ⲽ f(x)=2cos^2 x+3 sin2x+a =cos2x+3 sin2x+a+1 =2(1/2cos2x+3 /2sin2x)+a+1 =2(sin/6cos2x+cos/6sin2x)+a+1 =2sin(/6+2x)+a+1 Ϊx[0,/2] 2sin(/6+2x)...

1.ĸΪsin2xԭʽΪ[4cos2x/sin^22x]dx 2.лԪ2xΪt,ԭʽΪ[2cos2x/sin^2t]dt. 3Ԫ,ɹ۲쵽sin t'=cost.ԭʽ2[1/sin^2t]dsint. 4.óΪ-2/sint+c 5.tΪ2xУ-2/sin...

hexiao0818cos[A+/4]ʱ,. /2 < A+ /4 < /2 + /4 cos[A+/4]

1) f(x)=2a*b-1=2(cos2x)^2-23*sin2xcos2x-1 =(1+cos4x)-3*sin4x-1 =cos4x-3sin4x =2cos(4x+/3) ԣf(x) СֵΪ -2 ʱ 4x+/3=(2k+1)УkZ ˣf(x)ȡСֵʱxļ x|x=k/2+/6kZ 2f(x)ͼƽ...

1-cosxcos2xcos3x=1-cosx(1-2sin^2x)(cosxcos2x-sinxsin2x) =1-cosx(1-2sin^2x)[cosx(1-2sin^2x)-2sin^2xcosx] =1-cos^2x(1-2sin^2x)(1-4sin^2x) =1-(1-sin^2x)(1-2sin^2x)(1-4sin^2x) =8sin^6x-14sin^4x+7sin^2x sinxxΪȽС...

⣺ɵúgx=3sin2x+cos2x=2sin2x+6 ֱy=-a[02]㣮x[02]2x+6[676]gx[-12]2x+6=tt[676]y=ht=2sint ֱy=m[676]㣬ͼҪʹ...

⣺ Ϊabƽ 3cosx=4sinx tanx=sinx/cosx=3/4 sin2x-2cos²x =(2sinxcosx-2cos²x)/(sin²x+cos²x) ӷĸͬʱcos²x =(2tanx-2)/(tan²x+1) =(23/4-2)/[(3/4)²+1] =(-1/2)/(25/16) =-8...

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