Źródło TeX:

f^\prime(x)=\left(\operatorname{arcctg}(x^6)\right)^\prime=-\frac {1}{1+\left(x^6\right)^2}\cdot \left(x^6\right)^\prime=-\frac {1}{1+x^{12}}\cdot 6x^5 =-\frac {6x^5}{1+x^{12}}