We are given #f(x)=(e^tan(1/x))^(1/2)#
#f'(x)=d/dx[(e^tan(1/x))^(1/2)]#
#color(white)(f'(x))=1/2*(e^tan(1/x))^(1/2-1)*d/dx[e^tan(1/x)]#
#color(white)(f'(x))=1/2*(e^tan(1/x))^(1/2-1)*e^tan(1/x)*d/dx[tan(1/x)]#
#color(white)(f'(x))=1/2*(e^tan(1/x))^(1/2-1)*e^tan(1/x)*sec^2(1/x)*d/dx[x^(-1)]#
#color(white)(f'(x))=1/2* (e^tan(1/x))^(1/2-1)* e^tan(1/x)* sec^2(1/x)* -1* x^(-1-1)#
#color(white)(f'(x))=(-(e^tan(1/x))^(-1/2)e^tan(1/x)sec^2(1/x)x^(-2))/2#
#color(white)(f'(x))=(-e^tan(1/x)sec^2(1/x))/(2x^2sqrt((e^tan(1/x))))#
#color(white)(f'(x))=-(e^tan(1/x)sec^2(1/x))/(2x^2sqrt((e^tan(1/x))))#