Question about Taylor Series While loop.

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Derryn
Derryn 2013-3-6
I'm completely stuck on this While Loop using Taylor Series.
x = input('Input the angle in radians: ');
Cos_Estimate = 0;
k = 0;
Errrr = 1
while Errrr > .000001
if mod(k,2)
Sign = 1;
else
Sign = -1;
end
k = k + 2;
Cos_Estimate = Cos_Estimate + (x^k/(factorial(k)*Sign));
Errrr = abs(Cos_Estimate - cos(x));
end
err = abs(Cos_Estimate - cos(x));
fprintf('The estimated cosine value based on the Taylor Series is: %0.6f \n',Cos_Estimate)
fprintf('The actual cosine value is : %0.6f \n',cos(x))
fprintf('The estimation error is: %0.6f \n',err)
fprintf('The number of terms required was: \n',term)
Now I am getting NaN for my variable. I'm stuck.

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采纳的回答

Azzi Abdelmalek
Azzi Abdelmalek 2013-3-6
编辑：Azzi Abdelmalek 2013-3-6
Try this
x = input('Input the angle in radians: ');
Cos_Estimate = 1;
Errrr=1
Sign = 1;
k = 0;
while Errrr > .000001 & k<60
Sign =-Sign;
k = k + 2;
Cos_Estimate = Cos_Estimate + (x^k/(factorial(k)*Sign))
Errrr = abs(Cos_Estimate - cos(x))
end
display(Cos_Estimate)

更多回答（2 个）

Babak
Babak 2013-3-6
add this line to the beginning of your code:
Errrr =1;
  1 个评论
Derryn
Derryn 2013-3-6
Added it, but now I get this as my output:
EDU>> Lab7_Prob3Script
Input the angle in radians: pi
The estimated cosine value based on the Taylor Series is: NaN
The actual cosine value is : -1.000000
The estimation error is: NaN
The number of terms required was:

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Azzi Abdelmalek
Azzi Abdelmalek 2013-3-6
编辑：Azzi Abdelmalek 2013-3-6
Your code never enter in the loop because Errrr is not defined
  5 个评论
显示 3更早的评论
Matt Kindig
Matt Kindig 2013-3-6
编辑：Matt Kindig 2013-3-6
Also, what exactly is the point of the "estimation error" calculation (calculation of 'err')? By definition, won't this be equal to Errrr, because you have defined it that way? Also, won't 'err' always be less than 0.000001, because of the way you have defined your loop?
Derryn
Derryn 2013-3-6
Ah ok thanks. Does this look better?
x = input('Input the angle in radians: ');
Cos_Estimate = 0; k = 0;
count = 0;
Errrr = 1;
while Errrr > .000001
count = count + 1;
if mod(k,2)
Sign = 1;
else
Sign = -1;
end
k = k + 2;
Cos_Estimate = Cos_Estimate + (x^k/(factorial(k)*Sign));
Errrr = abs(Cos_Estimate - cos(x));
if k > 170
break
end
end
err = abs(Cos_Estimate - cos(x));
fprintf('The estimated cosine value based on the Taylor Series is: %0.6f \n',Cos_Estimate)
fprintf('The actual cosine value is : %0.6f \n',cos(x))
fprintf('The estimation error is: %0.6f \n',err)
fprintf('The number of terms required was: %0.0f \n',count)
I'm still getting the wrong value for Cos_Estimate

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