First, you used 2 to multiply by 1:
Then, you used to add 0:
Then, you split and :
And as you can see in the end, all this work was an elaborate plan to achieve a cancellation and split it into two easier integrals:
First integral should be simple enough for you, and as for the second integral, you should see that by taking 2 out as a factor and doing some manipulation, you'll get a standard arctan form.