You will need the second derivative of that lovely expression.
Substitute into the Differential equation.
After a little algebra, you should be able to demonstrate equality.
That's all there is to it.
First off, I read the sticky, I hope to understand it all one day
I am supposed to verify the the solution of the differential equation:
Solution: -cosx ln abs(secx + tan x). The equation is y" +y = tanx
Now, I have the solution spelled out in my answer guide, but I don't know how they got from step to step (just so you know I'm not looking for an answer handout)