sin^2 x-cos^2 x=cos
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sin^2x-cos^2x=cossin^2x-cos^2x=cossin^2x-cos^2x=cos1-cos²x-cos²x=cosx2cos²x+cosx-1=0(
sin^2 x-cos^2 x=cos
sin^2 x-cos^2 x=cos
sin^2 x-cos^2 x=cos
1-cos²x-cos²x=cosx
2cos²x+cosx-1=0
(cosx+1)(2cosx-1)=0
cosx=-1或cosx=1/2
cosx=-1时,sinx=0
cosx=1/2时,sinx=±根号3/2
y=2cos x (sin x+cos x)
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sin(2x+45)=cos
2cos x (sin x -cos x)+1