Step 1

Given

\(\displaystyle{y}={\cot{{7}}}{x}^{{{3}}}\)

To find

\(y'.\)

Step 2

\(\displaystyle{\frac{{{d}}}{{{\left.{d}{x}\right.}}}}{\left({\cot{{x}}}\right)}=-{\cos{{e}}}{c}^{{{2}}}{x}\)

\(\displaystyle{y}'=-{\cos{{e}}}{x}{\left({7}{x}^{{{3}}}\right)}\times{21}{x}^{{{2}}}\)

\(\displaystyle=-{21}{x}^{{{2}}}{\cos{{e}}}{c}^{{{2}}}{\left({7}{x}^{{{3}}}\right)}\).