easy question : why i get NaN here ?

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yahya elyan
yahya elyan 2020-5-30
回答： Walter Roberson 2020-5-31
>> 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)
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yahya elyan
yahya elyan 2020-5-30
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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采纳的回答

yahya elyan
yahya elyan 2020-5-30
try using
U=1/(1+limit((K/(H*((J*H+b)*(L*H+R)+K^2))),H,0,'right'));
  2 个评论
madhan ravi
madhan ravi 2020-5-30
编辑：madhan ravi 2020-5-30
It is solved but do you know the reason for NaN xD? Because your original question asks “why...?”
yahya elyan
yahya elyan 2020-5-30
编辑：yahya elyan 2020-5-30
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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更多回答（1 个）

Walter Roberson
Walter Roberson 2020-5-31
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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