Consider the integral

$/20$

$$cos$2($x$)$dx

Which is the appropriate method to use for this integral?

Use the substitution

u $=$ cos$($x$).$

Use a product to sum identity.$$Use the identity

sin$2($x$)=$

$12$

$$

$12$

cos$(2$x$).$

Use the identity

cos$2($x$)=$

$12$

$+$

$12$

cos$(2$x$).$

Use the substitution

u $=$ sin$($x$).$

Compute the integral. Do not use machine assistance. Provide an exact result rather than a decimal approximation.

$/20$

$$cos$2($x$)$dx $=$