f(x) = 2x*sin(1/x) - cos(1/x)
f ' (x) (hast du ? ) = (-2/x) * cos(1/x) - ( 1/x^2) * sin(1/x) + 2 sin(1/x )
f ' ' (x) = (2/x^2 )*cos(1/x) - (2/x^3)*sin(1/x) - ( - (2/x^3)*sin(1/x) - (1/x^4)*cos(1/x) ) - (2/x^2 )*cos(1/x)
= - (2/x^3)*sin(1/x) - ( - (2/x^3)*sin(1/x) - (1/x^4)*cos(1/x) )
= - (2/x^3)*sin(1/x) + (2/x^3)*sin(1/x) + (1/x^4)*cos(1/x)
= (1/x^4)*cos(1/x)
f ' ' ' (x) = (1/x^6)*sin(1/x) - ( 4/x^5 ) * cos(1/x)