Hi, I'm new here. I had a question on the thought process for this integral. I know what the answer is, I just don't see how to get to a certain step. The question is:

I checked the steps on wolframalpha, which said to rewrite the integral as:

Okay, I understand that, but then it says to rewrite that integral as:

I don't understand this last step. Is there an identity that I'm not seeing? Any help is appreciated.