Problem with integration need help
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Hi guys,
The next code is to solve an integration. The code will keep running without show any result. Please, need your help if you know the reason.
The code is;
syms T1 T2 r1 r2 r w m k Tb
clc
b=(-4*m*w^2*r1^4)/(k*(r2^2-r1^2));
c1=((T2-T1)+(b*r2^2/4)*(((r2/r1)^2)-1))/(log(r2/r1));
c2=T1-((b*r2^4)/(4*r1^2))-(((T2-T1)+(b*r2^2/4)*(((r2/r1)^2)-1))/(log(r2/r1)))*log(r1);
Tb=(int((((c1*r/2)+(c2/r))*((b*r2^4/4*r^2)+(c1*log(r)+c2))*r),r,r1,r2))/....
(int(((((-2*w*r1^2)/(r2^2-r1^2))*(r/2))+(((w*r1^2*r2^2)/(r2^2-r1^2))*(1/r)))*r,r,r1,r2));
采纳的回答
Walter Roberson
2013-12-20
1 个投票
Try breaking Tb up into two pieces, numerator and denominator, so that you can figure out which of the two integrations is giving the problem.
In my tests with a different mathematics system, the integrations were fast.
2 个评论
Abdulaziz
2013-12-20
Walter Roberson
2013-12-20
In both your original equation and the modified one you give about half an hour ago, none of the b, c1, or c2 involve "r". Because of that, you can do the integration just by
syms b c1 c2 r1 r2 r
Tb1 = int((((c1*r/2)+(c2/r))*((b*r2^4/4*r^2)+(c1*log(r)+c2))*r),r,r1,r2);
and then take that result and substitute in the values for b, c1, c2:
b=(-4*m*w^2*r1^4)/(k*(r2^2-r1^2));
c1=((T2-T1)+(b*r2^2/4)*(((r2/r1)^2)-1))/(log(r2/r1));
c2=T1-((b*r2^4)/(4*r1^2))-(((T2-T1)+(b*r2^2/4)*(((r2/r1)^2)-1))/(log(r2/r1)))*log(r1);
Tb = subs(Tb1);
As the integral will be simpler, it is less likely that it will run indefinitely.
更多回答（1 个）
Abdulaziz
2013-12-20
编辑：Walter Roberson
2013-12-20
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