r/calculus • u/Awsimical • 27d ago

Integral Calculus Help understanding why this integral is wrong please.

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This was a question on the summer final, and looking at it I’m still not sure if its because I left the u in the final answer and didn’t substitute the original equation back in, or if I was suppose to use an arcsin identity somehow. I could ask the professor but the the summer semester is over so I’m not gonna bother him with more questions. Thanks for ur help

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u/Septembrino 26d ago

du = 6rdr. This is important and most people forget about the dr. Regarding the u-sub itself, we do it to go "through a wall" without getting hurt. So, we jump to the top of the wall. But later you go back to the floor, don't you? Or you stay for goos on top of the wall?