Find minimum of single-variable function

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Mark S
Mark S 2021-1-25
评论： Adam Danz 2021-1-26
Hi, what expression is calculated by the following command in Matlab?
Code:
fminbnd(@(x) (sin(x).^2-1),0,pi)
Minimum of:
(a) f(x)=1-sin x^2 or (b)1-sin^2x.
I answered a) in my exercise, however I am not sure if this is correct. Can someone tell me if this is correct?
  2 个评论
Adam Danz
Adam Danz 2021-1-25
Sounds like homework.
The documentation should be helpful to understand what that function is doing,
https://www.mathworks.com/help/matlab/ref/fminbnd.html
Mark S
Mark S 2021-1-25
编辑：Mark S 2021-1-25
Thank you for your help. I have answered a) in my exam, it would be nice if you can say if it's right or not. Because also with the link that you have mentioned i am not sure if my answer was right or not :/

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回答（1 个）

Adam Danz
Adam Danz 2021-1-25
Hint:
[x,fval] = fminbnd(___)
gives you the (x,y) values at the minimum.
You could plug the x values into both of your options and the one that returns the matching y value is the correct function.
  2 个评论
Mark S
Mark S 2021-1-25
编辑：Mark S 2021-1-25
Ok, for x i get 4.5994e-05 and for fval =-1.0000
I put x into a) f(x)=1-sin4.5994e-05^2=1
I put x into b) f(x)=1-sin^2 *4.5994e-05=1
I get for same 1. But I think this cant't be right...
Adam Danz
Adam Danz 2021-1-26
Could you share the 2 lines of code where you tested the two versions? There's probably an error in how you're setting the equations.

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