Calculating this difficult integral (equation of a circle)

  • Context: Graduate 
  • Thread starter Thread starter Mad_MechE
  • Start date Start date
  • Tags Tags
    Circle Integral
Click For Summary

Discussion Overview

The discussion revolves around the calculation of two integrals derived from the equation of a circle. Participants explore methods to solve these integrals, specifically focusing on the functions h(x) and their respective integrals: \(\int\frac{1}{h(x)^2}dx\) and \(\int\frac{1}{h(x)^3}dx\). The context includes attempts to use software tools like Maple and Mathematica for symbolic computation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses difficulty in calculating the integrals and seeks assistance, mentioning their attempts with Maple and Mathematica.
  • Another participant provides a lengthy symbolic output from Maple for the first integral, which includes complex functions and arctanh terms.
  • A third participant shares a similarly complex output for the second integral, also generated by Maple, indicating the complexity of the expressions involved.
  • A later reply emphasizes the need for a symbolic answer that can be directly used in MATLAB, expressing frustration with the outputs from Maple that are not easily transferable.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the necessity of symbolic answers versus numerical solutions. There is a clear disagreement on the usability of the outputs from Maple, with some participants finding them unmanageable for their needs.

Contextual Notes

The discussion highlights limitations in the outputs generated by computational tools, particularly regarding their format and usability in MATLAB. There is also an implicit assumption that a symbolic solution is preferable for further validation and application.

Mad_MechE
Messages
6
Reaction score
0
I have tried numerous methods to calculate this integral and can't seem to figure it out.
I have tried to use maple and mathematica but i am not very strong using these programs. I was wondering if someone would be able to help me solve this integral. This equation stemmed from the equation of a circle... and i got the following function:

[tex]h = h0 + R - \sqrt{R+x}\sqrt{R-x}[/tex]

i am trying to integrate the following:
[tex]\int\frac{1}{h(x)^2}dx[/tex]

and

[tex]\int\frac{1}{h(x)^3}dx[/tex]

Thanks for all your help

MT
 
Physics news on Phys.org
Do you really need symbolic answers? For the first one, Maple says:
[tex] -1/2\, \left( 2\,i{R}^{3}{\it h0}\,{\rm arctanh} \left( {\frac {{R}^{2<br /> }+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{ \left( {\it h0}+R \right) <br /> \sqrt {{R}^{2}-{x}^{2}}}} \right) +2\,i{R}^{3}{\it h0}\,{\rm arctanh}<br /> \left( {\frac {-{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{<br /> \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) -4\,{R}^{<br /> 3}{\it h0}\,\arctan \left( {\frac {x}{\sqrt {{\it h0}}\sqrt {{\it h0}+<br /> 2\,R}}} \right) +i{R}^{2}{{\it h0}}^{2}{\rm arctanh} \left( {\frac {{R<br /> }^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{ \left( {\it h0}+R<br /> \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) +i{R}^{2}{{\it h0}}^{2}{<br /> \rm arctanh} \left( {\frac {-{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{<br /> \it h0}}x}{ \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}}<br /> \right) -2\,{R}^{2}\arctan \left( {\frac {x}{\sqrt {{\it h0}}\sqrt {{<br /> \it h0}+2\,R}}} \right) {{\it h0}}^{2}-2\,{R}^{2}x\sqrt {{\it h0}}<br /> \sqrt {{\it h0}+2\,R}+i{R}^{2}{\rm arctanh} \left( {\frac {-{R}^{2}+i<br /> \sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{ \left( {\it h0}+R \right) <br /> \sqrt {{R}^{2}-{x}^{2}}}} \right) {x}^{2}+i{R}^{2}{\rm arctanh}<br /> \left( {\frac {{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{<br /> \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) {x}^{2}-2<br /> \,{R}^{2}\arctan \left( {\frac {x}{\sqrt {{\it h0}}\sqrt {{\it h0}+2\,<br /> R}}} \right) {x}^{2}-4\,Rx{{\it h0}}^{3/2}\sqrt {{\it h0}+2\,R}-2\,R<br /> \sqrt {R-x}\sqrt {R+x}\sqrt {{\it h0}}\sqrt {{\it h0}+2\,R}x-2\,x{{<br /> \it h0}}^{5/2}\sqrt {{\it h0}+2\,R}-2\,\sqrt {R-x}\sqrt {R+x}{{\it h0}<br /> }^{3/2}\sqrt {{\it h0}+2\,R}x \right) \left( {\it h0}+2\,R \right) ^{<br /> -3/2}{{\it h0}}^{-3/2} \left( {{\it h0}}^{2}+2\,{\it h0}\,R+{x}^{2}<br /> \right) ^{-1}[/tex]
 
and for the second one, Maple says:
[tex] 1/4\, \left( -12\,i{R}^{4}{\it h0}\,{\rm arctanh} \left( {\frac {{R}^{<br /> 2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{ \left( {\it h0}+R<br /> \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) {x}^{2}-12\,i{R}^{4}{\it h0<br /> }\,{\rm arctanh} \left( {\frac {-{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {<br /> {\it h0}}x}{ \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}}<br /> \right) {x}^{2}-18\,i{R}^{3}{{\it h0}}^{2}{\rm arctanh} \left( {<br /> \frac {{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{ \left( {\it <br /> h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) {x}^{2}-18\,i{R}^{3}{{<br /> \it h0}}^{2}{\rm arctanh} \left( {\frac {-{R}^{2}+i\sqrt {{\it h0}+2\,<br /> R}\sqrt {{\it h0}}x}{ \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}<br /> }}} \right) {x}^{2}-6\,i{R}^{2}{{\it h0}}^{3}{\rm arctanh} \left( {<br /> \frac {-{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{ \left( {\it <br /> h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) {x}^{2}-6\,i{R}^{2}{{<br /> \it h0}}^{3}{\rm arctanh} \left( {\frac {{R}^{2}+i\sqrt {{\it h0}+2\,R<br /> }\sqrt {{\it h0}}x}{ \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}<br /> }} \right) {x}^{2}-3\,i{R}^{2}{\it h0}\,{\rm arctanh} \left( {\frac {{<br /> R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{ \left( {\it h0}+R<br /> \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) {x}^{4}-3\,i{R}^{2}{\it h0}<br /> \,{\rm arctanh} \left( {\frac {-{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{<br /> \it h0}}x}{ \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}}<br /> \right) {x}^{4}+6\,\sqrt {R+x}\sqrt {R-x}{{\it h0}}^{9/2}\sqrt {{\it <br /> h0}+2\,R}x+2\,\sqrt {R+x}\sqrt {R-x}{{\it h0}}^{5/2}\sqrt {{\it h0}+2<br /> \,R}{x}^{3}+4\,{{\it h0}}^{11/2}\sqrt {{\it h0}+2\,R}x+24\,{R}^{5}<br /> \arctan \left( {\frac {x}{\sqrt {{\it h0}}\sqrt {{\it h0}+2\,R}}}<br /> \right) {{\it h0}}^{2}+30\,{R}^{3}\arctan \left( {\frac {x}{\sqrt {{<br /> \it h0}}\sqrt {{\it h0}+2\,R}}} \right) {{\it h0}}^{4}+48\,{R}^{4}<br /> \arctan \left( {\frac {x}{\sqrt {{\it h0}}\sqrt {{\it h0}+2\,R}}}<br /> \right) {{\it h0}}^{3}+6\,{R}^{3}\arctan \left( {\frac {x}{\sqrt {{<br /> \it h0}}\sqrt {{\it h0}+2\,R}}} \right) {x}^{4}+6\,{R}^{2}\arctan<br /> \left( {\frac {x}{\sqrt {{\it h0}}\sqrt {{\it h0}+2\,R}}} \right) {{<br /> \it h0}}^{5}+20\,{R}^{4}{{\it h0}}^{3/2}\sqrt {{\it h0}+2\,R}x+6\,{R}^<br /> {3}\sqrt {{\it h0}}\sqrt {{\it h0}+2\,R}{x}^{3}+46\,{R}^{3}{{\it h0}}^<br /> {5/2}\sqrt {{\it h0}+2\,R}x+42\,{R}^{2}{{\it h0}}^{7/2}\sqrt {{\it h0}<br /> +2\,R}x+6\,{R}^{2}{{\it h0}}^{3/2}\sqrt {{\it h0}+2\,R}{x}^{3}+20\,{{<br /> \it h0}}^{9/2}\sqrt {{\it h0}+2\,R}xR+36\,{R}^{3}\arctan \left( {<br /> \frac {x}{\sqrt {{\it h0}}\sqrt {{\it h0}+2\,R}}} \right) {{\it h0}}^{<br /> 2}{x}^{2}+6\,{R}^{2}\arctan \left( {\frac {x}{\sqrt {{\it h0}}\sqrt {{<br /> \it h0}+2\,R}}} \right) {\it h0}\,{x}^{4}+12\,{R}^{2}\arctan \left( {<br /> \frac {x}{\sqrt {{\it h0}}\sqrt {{\it h0}+2\,R}}} \right) {{\it h0}}^{<br /> 3}{x}^{2}+24\,{R}^{4}\arctan \left( {\frac {x}{\sqrt {{\it h0}}\sqrt {<br /> {\it h0}+2\,R}}} \right) {\it h0}\,{x}^{2}-12\,i{R}^{5}{{\it h0}}^{2}{<br /> \rm arctanh} \left( {\frac {-{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{<br /> \it h0}}x}{ \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}}<br /> \right) -12\,i{R}^{5}{{\it h0}}^{2}{\rm arctanh} \left( {\frac {{R}^{<br /> 2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{ \left( {\it h0}+R<br /> \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) -24\,i{R}^{4}{{\it h0}}^{3}<br /> {\rm arctanh} \left( {\frac {-{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{<br /> \it h0}}x}{ \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}}<br /> \right) -24\,i{R}^{4}{{\it h0}}^{3}{\rm arctanh} \left( {\frac {{R}^{<br /> 2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{ \left( {\it h0}+R<br /> \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) -15\,i{R}^{3}{{\it h0}}^{4}<br /> {\rm arctanh} \left( {\frac {-{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{<br /> \it h0}}x}{ \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}}<br /> \right) -15\,i{R}^{3}{{\it h0}}^{4}{\rm arctanh} \left( {\frac {{R}^{<br /> 2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{ \left( {\it h0}+R<br /> \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) -3\,i{R}^{3}{\rm arctanh}<br /> \left( {\frac {{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{<br /> \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) {x}^{4}-3<br /> \,i{R}^{3}{\rm arctanh} \left( {\frac {-{R}^{2}+i\sqrt {{\it h0}+2\,R}<br /> \sqrt {{\it h0}}x}{ \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}<br /> } \right) {x}^{4}-3\,i{R}^{2}{{\it h0}}^{5}{\rm arctanh} \left( {<br /> \frac {-{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {{\it h0}}x}{ \left( {\it <br /> h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}} \right) -3\,i{R}^{2}{{\it h0}}<br /> ^{5}{\rm arctanh} \left( {\frac {{R}^{2}+i\sqrt {{\it h0}+2\,R}\sqrt {<br /> {\it h0}}x}{ \left( {\it h0}+R \right) \sqrt {{R}^{2}-{x}^{2}}}}<br /> \right) +20\,{R}^{3}\sqrt {R+x}\sqrt {R-x}{{\it h0}}^{3/2}\sqrt {{<br /> \it h0}+2\,R}x+34\,{R}^{2}\sqrt {R+x}\sqrt {R-x}{{\it h0}}^{5/2}\sqrt <br /> {{\it h0}+2\,R}x+24\,R\sqrt {R+x}\sqrt {R-x}{{\it h0}}^{7/2}\sqrt {{<br /> \it h0}+2\,R}x+4\,R\sqrt {R+x}\sqrt {R-x}{{\it h0}}^{3/2}\sqrt {{\it <br /> h0}+2\,R}{x}^{3}+6\,{R}^{2}\sqrt {R+x}\sqrt {R-x}\sqrt {{\it h0}}<br /> \sqrt {{\it h0}+2\,R}{x}^{3} \right) \left( -x+i\sqrt {{\it h0}+2\,R}<br /> \sqrt {{\it h0}} \right) ^{-2} \left( x+i\sqrt {{\it h0}+2\,R}\sqrt {{<br /> \it h0}} \right) ^{-2} \left( {\it h0}+2\,R \right) ^{-5/2}{{\it h0}}^<br /> {-5/2}[/tex]
but this window doesn't show the whole thing in either case.
 
unfortunately i do need a symbolic answer that i can use in matlab... every time i used maple i couldn't get an output i could copy and paste into MATLAB to use and i have no way to validate the solution from maple... thank you for your help!
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 29 ·
Replies
29
Views
5K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 6 ·
Replies
6
Views
3K