I have this equation

So I refer to a triangle and use these values for substitution.

= 5 cos(x)

x = 5 sin(x)

dx = 5 sin(x) = 5 cos(x)

I ended up having something like this.

I canceled the 5 sin(x)s leaving me with

integral(5 cos x) = - 5 sin x + c

I looked at the triangles and got back.

x/5 + c

Then I looked back at the book for answers and I was way way way off.

What did I do that was totally wrong?