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Mathematics Calculus Wolfram Language

Integrate error: unable to prove integral limit is a real number

YU DUAN

Posted 3 years ago

1.Integrate::pwrl: Unable to prove that the integral limit {0,x} is a real number. Adding assumptions may help. 2.Solve boundary value problems with discrete variables. Clear["`"] b = 0.61; h[x_] := Piecewise[{{3 - 0.8x/b, 0 <= x < 1.60125}, {0.9, 1.60125 <= x <= 21}}] eq = 163y''''[x] - (0.6 \!\( \SubsuperscriptBox[\(\[Integral]\), \(0\), \(x\)]\(\((0.3 \((\((x // h)\)\ 11800x\ y[x]Tanh[ \FractionBox[\(1\), \(0.6\((x // h)\)\)]])\))\) \[DifferentialD]x\)\)) y''[ x] + (x // h)* 11800x y[x]Tanh[1/(0.6 (x // h))] + 0.04 D[(x // h) 11800x y[x]Tanh[1/(0.6(x // h))], x] - 0.60.3(x // h)* 11800x y[x]Tanh[1/(0.6(x // h))]*y'[x] == 0 sol = NDSolveValue[{eq, y'''[0] == 0.008, y''[0] == 0.002, y'[21] == 0, y[21] == 0}, y, {x, 0, 21}] Plot[sol[x], {x, 0, 21}, PlotRange -> All]

1.Integrate::pwrl: Unable to prove that the integral limit {0,x} is a real number. Adding assumptions may help.
2.Solve boundary value problems with discrete variables.

Clear["`*"]
b = 0.61;
h[x_] := Piecewise[{{3 - 0.8*x/b, 0 <= x < 1.60125}, {0.9, 
    1.60125 <= x <= 21}}]
eq = 163*y''''[x] - (0.6 \!\(
\*SubsuperscriptBox[\(\[Integral]\), \(0\), \(x\)]\(\((0.3 \((\((x // 
              h)\)\ *11800*x\ *y[x]*Tanh[
\*FractionBox[\(1\), \(0.6*\((x // 
                 h)\)\)]])\))\) \[DifferentialD]x\)\)) y''[
     x] + (x // h)* 11800*x* y[x]*Tanh[1/(0.6 (x // h))] + 
   0.04 D[(x // h) *11800*x *y[x]*Tanh[1/(0.6*(x // h))], x] - 
   0.6*0.3*(x // h)* 11800*x *y[x]*Tanh[1/(0.6*(x // h))]*y'[x] == 0
sol = NDSolveValue[{eq, y'''[0] == 0.008, y''[0] == 0.002, 
   y'[21] == 0, y[21] == 0}, y, {x, 0, 21}]
Plot[sol[x], {x, 0, 21}, PlotRange -> All]

POSTED BY: YU DUAN

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YU DUAN

Posted 3 years ago

Thanks for the answer. Clear["`"] b=0.61; h[x_]:=Piecewise[{{3-0.8x/b,0<=x<1.60125},{0.9,1.60125<=x<=21}}] eq=163y''''[x]-(0.6 )y''[x]+(x//h) 11800x y[x]Tanh[1/(0.6(x//h))]+0.04 D[(x//h) 11800x y[x]Tanh[1/(0.6(x//h))],x]-0.60.3(x//h)* 11800x y[x]Tanh[1/(0.6(x//h))]*y'[x]==0 sol=NDSolveValue[{eq,y'''[0]==0.008,y''[0]==0.002,y'[21]==0,y[21]==0},y,{x,0,21}] Plot[sol[x],{x,0,21},PlotRange->All]

Thanks for the answer.

Clear["`*"]
b=0.61;
h[x_]:=Piecewise[{{3-0.8*x/b,0<=x<1.60125},{0.9,1.60125<=x<=21}}]
eq=163*y''''[x]-(0.6  )y''[x]+(x//h)* 11800*x* y[x]*Tanh[1/(0.6(x//h))]+0.04 D[(x//h) *11800*x *y[x]*Tanh[1/(0.6*(x//h))],x]-0.6*0.3*(x//h)* 11800*x *y[x]*Tanh[1/(0.6*(x//h))]*y'[x]==0
sol=NDSolveValue[{eq,y'''[0]==0.008,y''[0]==0.002,y'[21]==0,y[21]==0},y,{x,0,21}]
Plot[sol[x],{x,0,21},PlotRange->All]

POSTED BY: YU DUAN

Rohit Namjoshi

Posted 3 years ago

There are still problems. Copy the code you posted, paste it into Mathematica and try to evaluate it. There are missing `;` and the definition of `h` is missing. Take a look at the "Code Formatting" section here.

POSTED BY: Rohit Namjoshi

Rohit Namjoshi

Posted 3 years ago

Please format the code as `InputForm` code using the `< >` button in the toolbar so it can be copied/pasted and evaluated. If you copy/paste the code above, it will not evaluate.

POSTED BY: Rohit Namjoshi

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