Chapter 2 - The Derivative - 2.5 Derivatives of Trigonometric Functions - Exercises Set 2.5 - Page 151: 8

$f'(x)=2x\sec x+(x^2+1)(\sec x\tan x)$

$f(x)=(x^2+1)secx$ $f'(x)=\frac{d}{dx}(x^2+1)\times{secx}+(x^2+1)\times{\frac{d}{dx}(secx)}$ $f'(x)=(2x)\times{secx}+(x^2+1)\times{(secxtanx)}$ $f'(x)=2x\sec x+(x^2+1)(\sec x\tan x)$