Help with an integral

Main Question or Discussion Point

i have to integrate to find the electric potential due to a disk of charge with an uneven charge distribution. i was able to set up the intergral but i cant solve it. should i do integration by parts (i tried it) or use something else. just give me a hint

int ( r^3/[(x^2 + r^2)]^.5) dr (x is a constant)

thanks
 

Answers and Replies

dextercioby
Science Advisor
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Make the substitution

[tex] r=x\sinh t [/tex]

Daniel.
 
Gib Z
Homework Helper
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>.< I don't know Daniels way, Id go with trigonometric substitution, tan theta = r/x. Draw a triangle, you see that the hypotnuse is your denominator. Just solve for everything and sub them in, it reduces to [tex]x^3\int \tan^3 \theta \sec \theta d\theta[/tex].
 
yea i figured it out. i did uv substitution, takeing u=r^2 and dx= r/(r^2+x^2) ^9.5)

thank you for everyone who gave advice. :D
 

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