设f=[sin(2/x)]=1+cosx,求f(x),f[cos(2/x)].

题目

设f=[sin(2/x)]=1+cosx,求f(x),f[cos(2/x)].
如题!

答案

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