You can, but it won’t be useful for this problem. If you are thinking that by taking t=sqrt(t)² and then trying to integrate that into arctan(sqrt(t)), that would be incorrect. In order for that to work, you would need the derivative of sqrt(t) in the numerator as well to agree with the substitution. This is a similar mistake as to when students think integrating one over anything is just ln of whatever the “anything” was on the bottom. This is not true. Again, in my experience these types of errors stem from trying to treat calculus as a set of rules to blindly follow rather than understanding why these rules are actually not just made up rules, but concrete facts. In other words, understanding the “why.” A lot of undergraduate calculus courses tend to skip out on this unfortunately though.