Could someone show me where I am going wrong? I need to solve this using varation of parameters.

First I found the solution to the homogeneous equation:

Next, (note that y' is hard to see in math form)**

Next I set this to 0:

This changes to:

Next I plugged into the Origioal DE for respectively.

My result is:

Second equation from before:

Solving these 2 equation for and I get:

Integrating:

Using the formula:

The solution should be:

This is according to wolfram alpha:http://www.wolframalpha.com/input/?i...y%3Dcos%28x%29