Hello, andy849!
Quotient Rule:
\(\displaystyle f'(x) \;=\;\dfrac{(x^2+1)^{\frac{1}{2}}\cdot 2\sec^2\!(x^3+2)\tan(x^3+2)3x^2 \;-\; \sec^2\!(x^3+2)\cdot\frac{1}{2}(x^2+1)^{-\frac{1}{2}}2x}{x^2+1}\)
\(\displaystyle f'(x) \;=\;\dfrac{6x^2(x^2+1)^{\frac{1}{2}}\sec^2\!(x^3+2)\tan(x^3+2) \;-\; x(x^2+1)^{-\frac{1}{2}}\sec^2\!(x^3+2)}{x^2+1}\)
Factor:
\(\displaystyle f'(x) \;=\;\dfrac{x(x^2+1)^{-\frac{1}{2}}\sec^2\!(x^3+2)\cdot\big[6x(x^2+1)\tan(x^3+2) \:-\: 1\big]}{x^2+1}\)
\(\displaystyle f'(x) \;=\;\dfrac{x\sec^2\!(x^3+2)\cdot \big[6x(x^2+1)\tan(x^3+2) - 1\big]}{(x^2+1)^{\frac{3}{2}}} \)