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F Cosx Cos2x

f(sinx)=3-cos2x =3-(1-2sin²x) =2+2sin²x 则: f(x)=2+2x² 所以, f(cosx)=2+2cos²x =2+1+cos2x =3+cos2x

∵f(sinx)=3-cos2x=3-(1-2sinx*sinx) ∴f(x)=3-(1-2x*x) =2+2x*x 或者:设sinx=t cos2x=1-2(sinx)^2=1-2t^2 f(sinx)=3-cos2x f(t)=3-(1-2t^2)=2t^2+2 把t改成x f(x)=2x^2+2 f(cosx)=2cos^2 x+2=1+cos2x+2=3+cos2x

f(sin15°)=f(cos(90°-15°))=f(cos75°)=cos(2×75°)=cos150°=-根号3/2 请采纳,谢谢

f(x)=(sinx+cosx)²+cos2x =sin²x+2sinxcosx+cos²x+cos2x =sin²x+cos²x+2sinxcosx+cos2x =1+2sinxcosx+cos2x =1+sin2x+cos2x =1+(sin2x+cos2x) =1+√2(√2/2sin2x+√2/2cos2x) =1+√2[cos(π/4)sin2x+sin(π/4)...

供参考。

解f(cosx) =f(sin(π/2-x)) =cos2(π/2-x)+1 =cos(π-2x)+1 =-cos2x+1

解:设t=2-cosx∈[1,3]cosx=2-tcos2x=2(cosx)^2-1=2(t-2)^2-1=2t^2-8t+7故有:f(t)=2t^2-8t+7+2-t=2t^2-9t+9,t∈[1,3]f(x-1)=2(x-1)^2-9(x-1)+9=2x^2-4x+4-9x+9+9=2x^2-13x+22(x∈[2,4])

用三角函数中的诱导公式进行转化,可转化问题已知条件直接代入求解即可 解:f(sin15°)=f(cos(900-150))=f(cos75°)=cos(2×750)=cos150°=负二分之根号三故答案为:负二分之根号三 如果满意记得采纳哦!你的好评是我前进的动力。(*^__^*)...

f(sinx)=cos2x+1 = 1-2sin²x+1 = 2 - 2sin²x 所以,f(x)=2-2x² 所以,f(cosx)=2-2cos²x=2sin²x

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