Question 969566
You've got it backwards.
How about {{{u=cos(x)}}}?
Then,
{{{du=-sin(x)dx}}}
{{{sin(x)dx=-du}}}
So then substituting,
{{{int((sin(x)/cos(x)),dx)=int((-1/u),du)}}}
Take it from there and finish.
Repost if you need more help.