- #1
doktorwho
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Homework Statement
Question:
To solve the integral ##\int \frac{1}{\sqrt{x^2-4}} \,dx## on an interval ##I=(2,+\infty)##, can we use the substitution ##x=\operatorname {arcsint}##?
Explain
Homework Equations
3. The Attempt at a Solution [/B]
This is my reasoning, the function ##\operatorname {arcsint}## can have values of ##t \in (-1,1)## because t doesn't fall anywhere else from that range and then follows that ##x \in (-\pi/2, +\pi/2)## which are the end values of the interval of ##t##. As the max point of intevral of ##x## is ##+\pi/2## which is roughly 1.57, this substitution can't be made as it doesn't even enter the original interval. Is this correct?
I have a couple of follow up question that I'm concerned about. I would be really glad if you can help me with them.
Say that the interval of ##x## that we got has some of its values from the original interval but not all, could we make the substitution then or only when they are all from there? Any special cases?
Thanks very much :)