Evaluate the Following Integrals:
(A) $\int x ^ { 3 } \cos \left( x ^ { 4 } + 1 \right) d x$

Essay

Evaluate the following integrals:
(a) $\int x ^ { 3 } \cos \left( x ^ { 4 } + 1 \right) d x$ (b) $\int \frac { \cos ( \sqrt { x } ) } { \sqrt { x } } d x$ (c) $\int \frac { \cos ( 1 / x ) } { x ^ { 2 } } d x$ (d) $\int \frac { \cos ( \arctan x ) } { 1 + x ^ { 2 } } d x$