Integrating sqrt(x2+9) - Help Appreciated

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SUMMARY

The discussion focuses on integrating the function sqrt(x² + 9). Users suggest various methods, including integration by parts, substitutions such as x = 3 sinh(u), and trigonometric substitution with x = 3 tan(θ). The latter method simplifies the integral to a more manageable form using sec(θ). These techniques are essential for solving integrals involving square roots of quadratic expressions.

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Homework Statement



hey guys i was wondering if anyone could show my how to intergrate sqrt(x2+9). any help would be greatfully appreciated. the sqaure root is over everything:rolleyes:

P.s i have looked at table of intergral but can't see one that looks similar.


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The Attempt at a Solution

 
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Use integration by parts with u=\sqrt{x^2+9} and dv=dx...
 
thanks but i have never used any of those methods before?
 
You haven't been taught integration by parts yet? Do you know substitutions, if so try x=3 \sinh u. If both these methods are alien to you they probably expect you to compare it to a standard integral somewhere listed in the back or front of your calculus book.
 
Yet another way is to let x= 3tan(\theta). Then dx= 3sec^2(\theta) and \sqrt{x^2+ 9}= \sqrt{9tan^2(\theta)+ 9}= 3\sqrt{tan^2(\theta)+ 1}= 3sec(\theta).
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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