Indefinite integral of arcsec(x)

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SUMMARY

The discussion focuses on the indefinite integral of arcsec(x), specifically the integral $$\int arcsec(x) \ dx$$. The user attempted to solve this integral by substituting and integrating by parts, ultimately arriving at an expression that differed from the result provided by Wolfram Alpha. However, it was concluded that both answers are correct, as they can be manipulated to show equivalence. The importance of the constant of integration in indefinite integrals was also highlighted.

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PWiz
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Just for fun, I tried this rather trivial problem, but I think I went wrong somewhere:
$$\int arcsec(x) \ dx$$
Let ##arcsec(x)=y## . Then ##x=sec \ y##, or ##y=arccos(\frac 1{x})##
So the problem becomes $$\int arccos(\frac 1 {x}) \ dx$$
Let ##\frac 1 {x} = cos \ u## , so that ##dx = secu \ tanu \ du##.
So the questions simplifies to ##\int u \ secu \ tanu \ du##. If I integrate by parts, then this equals to
$$u \int secu \ tanu \ du - \int (\int secu \ tanu \ du) du$$
Since ##\int secu \ tanu \ du = secu##, I get ##u \ secu - \int secu \ du##
##\int secu \ du = ln(\sqrt{\frac{1+sinu}{1-sinu}})##
Substituting the Xs, I get $$x \ arcsec(x) - ln(\sqrt{\frac{1+\sqrt{1-\frac{1}{x^2}}}{1-\sqrt{1-\frac{1}{x^2}}}}) + c= x \ arcsec(x) - ln(\sqrt{\frac{x+\sqrt{x^2-1}}{x-\sqrt{x^2-1}}}) + c $$
where ##c## is an arbitrary constant. I checked my answer with Wolfram Alpha here:
http://integrals.wolfram.com/index.jsp?expr=arcsec(x)&random=false
As you can clearly see, the answer is different from mine. In which step did I goof?
 
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PWiz said:
, I get $$x \ arcsec(x) - ln(\sqrt{\frac{1+\sqrt{1-\frac{1}{x^2}}}{1-\sqrt{1-\frac{1}{x^2}}}}) + c= x \ arcsec(x) - ln(\sqrt{\frac{x+\sqrt{x^2-1}}{x-\sqrt{x^2-1}}}) + c $$
where ##c## is an arbitrary constant. I checked my answer with Wolfram Alpha here:
http://integrals.wolfram.com/index.jsp?expr=arcsec(x)&random=false
As you can clearly see, the answer is different from mine. In which step did I goof?
Your all steps are correct, you have not goofed.
Wolfram's answer as well as your answer is correct. It's the way of manipulating.
Rearrange some terms in wolfram' answer and in yours. You will see both are same.

Edit [ Add] indefinite integration is an area where you get answers which are not matching by someone's else. The constant of integration has a big role here.
 
Okay, thanks!
 
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