easy question : why i get NaN here ?

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>> u=1/(1+limit(K/(w*(((J*w+b)*(L*w+R))+K^2)),w,0))
or
>> limit(K/(w*(((J*w+b)*(L*w+R))+K^2)),w,0)
  6 Comments
yahya elyan
yahya elyan on 30 May 2020
Edited: yahya elyan on 30 May 2020
UP
yahya elyan
yahya elyan on 30 May 2020
it can be solved by using
>>U=1/(1+limit((K/(H*((J*H+b)*(L*H+R)+K^2))),H,0,'right'));

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Accepted Answer

yahya elyan
yahya elyan on 30 May 2020
try using
U=1/(1+limit((K/(H*((J*H+b)*(L*H+R)+K^2))),H,0,'right'));
  2 Comments
madhan ravi
madhan ravi on 30 May 2020
Edited: madhan ravi on 30 May 2020
It is solved but do you know the reason for NaN xD? Because your original question asks “why...?”
yahya elyan
yahya elyan on 30 May 2020
Edited: yahya elyan on 30 May 2020
yah if i remember well it was about being unable to approach zero for solving limit so we usually took 0+ or 0- value thats a way instead of using lupital xD

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More Answers (1)

Walter Roberson
Walter Roberson on 31 May 2020
J = 0.01;
b = 0.0737;
K = 0.072;
R = 1.17;
L = 0.024;
syms w
temp = K/(w*(((J*w+b)*(L*w+R))+K^2));
tempc = collect(temp, w);
disp(tempc)
ans =
120000/(400*w^3 + 22448*w^2 + 152355*w)
Examing this, we see that as w approaches 0, the controlling expression would be the 152355*w part -- the w^3 and w^2 parts would vanish compared to the w component. So the limit of temp as w goes to 0 would be like
limit( (120000/152355)/w, w, 0)
When w approaches from the right, that is positive divided by +0, which is +infinity
When w approaches from the left, that is positive divided by -0, which is -infinity
Therefore the left and right limits are different, so the limit is not defined.

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