Evaluate the following integral.

${\displaystyle \underset{-4}{\overset{3}{}}}co{s}^{2}xdx$

$J,2$

$-4,J$

$-4$

Use a change $of$ variables $to$ evaluate the second $of$ these integrals. What $is$ the best choice $ofu$ for the change

$of$ variables?

$u=2x$

Find $du.$

$du=(2)dx$

Rewrite the second $of$ the two integrals found above using this change $of$ variables.

${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}(1)du$

$(Type$ exact answers.$)$