Lagrange Error Bound Practice Test

Approximating $f(\pi/6)$ with $T_4$ about $a=0$, given $|f^{(5)}(x)|\le 2$ for $x\in0,\pi/6$, find the maximum error.

For $f(x)=\cos x$, use $P_2(x)=1-\frac{x^2}{2}$ about $0$; if $|f^{(3)}(x)|\le 1$ on $0,0.4$, what maximum error at $x=0.4$?