f(sinx)=cos2x+1求f(cosx)

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f(sinx)=cos2x+1求f(cosx)
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f(sinx)=cos2x+1求f(cosx)
f(sinx)=cos2x+1求f(cosx)

f(sinx)=cos2x+1求f(cosx)
f(cosx)
=f[sin(π/2-x)]
=cos[2(π/2-x)]+1
=cos(π-2x)+1
=-cos2x+1

∵f(sinx)=cos2x+1
=1-2sin^2 x+1 [倍角公式〕
=2-2sin^2 x
∴f(x)=2-2x^2
∴f(cosx)=2-2cos^2 x
=2(1-cos^2 x)
=2sin^2 x

f(sinx)=2cosx方-1+1=2cosx方=2(1-sinx方)
既f(x)=2-2x方
所以f(cosx)=2-2cosx方