The indicated function

y$1($x$)$

is a solution of the following differential equation.

y$\text{'}\text{'}+100$y $=0$;$$y$1=$ cos$(10$x$)$

Use reduction of order, or the formula

y$2=$ y$1($x$)$

e$$P$($x$)$ dxy

$21$

$($x$)$

$$dx

as instructed, to find a second solution

y$2($x$).$

y$2=$