Solving Difficult Integral: Strategies & Tips

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SUMMARY

The discussion focuses on solving a challenging double integral with the integrand cos(x) * sqrt(3 + (cos(x))^2) dx dy, where the x bounds are from arctan(y) to pi/4 and the y bounds are from 0 to 1. Participants explored various methods, including integration by parts and converting to polar coordinates, but faced difficulties. The successful transformation of the integrand resulted in -sin(x) * sqrt(3 + (cos(x))^2) dx, which was further simplified using the Mathematica online integrator, yielding the expression (-3*ArcSinh[Cos[x]/Sqrt[3]])/2 - (Cos[x]*Sqrt[3 + Cos[x]^2])/2.

PREREQUISITES
  • Understanding of double integrals and their bounds
  • Familiarity with integration techniques such as integration by parts
  • Knowledge of polar coordinate transformations
  • Experience using Mathematica for symbolic integration
NEXT STEPS
  • Study the method of integration by parts in detail
  • Learn about converting rectangular coordinates to polar coordinates in integrals
  • Explore the capabilities of Mathematica for solving complex integrals
  • Investigate trigonometric substitution techniques for integrals involving square roots
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Students and educators in calculus, mathematicians tackling complex integrals, and anyone interested in advanced integration techniques and tools like Mathematica.

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Homework Statement


The whole integral is a double integral, but I can't even perform the first integration.

The integrand is cosx*sqrt(3+(cosx)^2) dxdy
The x bounds are from arctan(y) to pi/4
the y bounds are from 0 to 1

Homework Equations


Converting rectangular to polar may help.

The Attempt at a Solution



I've tried parts, but it was a disaster. I also started converting it to polar, but that was also a disaster.
 
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I switched dx and dy and the bounds.

The new y bounds are from 0 to tanx
The new x bounds are from 0 to pi/4

The resulting integrand after successfully integrating in terms of y is

-sinx*sqrt(3 + (cosx)^2) dx

It's a little nicer, but still ugly.

Putting the integrand into the mathematica online integrator, I get this:

(-3*ArcSinh[Cos[x]/Sqrt[3]])/2 - (Cos[x]*Sqrt[3 + Cos[x]^2])/2

How do I get here? I tried by starting with parts, but it doesn't get me far.
 
Solved with trig substitution and then parts.
 

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