how to find the integral of F = x./(1+x.^4) on matlab

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jey sun
jey sun 2014-3-26
评论： Roger Stafford 2014-3-27
how to find the integral of F = x./(1+x.^4) on matlab in the range of 0 and 5 i have used the following; int(F,x,0,6)
but an error of "Undefined function 'int' for input arguments of type 'double'." comes up.
  1 个评论
Roger Stafford
Roger Stafford 2014-3-27
Note that this a problem you don't really need matlab for. A calculus student would tell you to substitute y = x^2 to produce the integral of 1/2/(1+y^2) with respect to y from y = 0 to y = 6^2 which gives you 1/2*atan(36).

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回答（2 个）

Star Strider
Star Strider 2014-3-26
Use the integral function:
F = @(x) x./(1+x.^4)
C = integral(F, 0, 6)
produces:
C =
771.5128e-003
John D'Errico
John D'Errico 2014-3-27
IF you have the symbolic toolbox, then do this:
syms x
int(x/(1+x^4),x,0,6)
ans =
atan(36)/2
If not, then do it numerically.
format long g
integral(@(x) x./(1 + x.^4),0,6)
ans =
0.771512845100738
Note that the numerical solution happens to match the symbolic one. A good thing, really.
atan(36)/2
ans =
0.771512845100738

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