The Taylor series for $f(x) = \ln(\sec(x))$ at $a = 0$ is $\displaystyle \sum_{n=0}^\infty c_n( x )^n.$
Find the first few coefficients.
$c_0 =$
$c_1 =$
$c_2 =$
$c_3 =$
$c_4 =$
Find the exact error in approximating $\ln(\sec(-0.3))$ by its fourth degree Taylor polynomial at $a = 0 .$
The error is