Empty sym: 0-by-1

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Amory Tillinghast-Raby
评论： Walter Roberson 2020-1-4
I am really really new to matlab and essentially just playing around with it. However, I have come across an issue that I am not fully sure how to resolve.
My code is incredibly simple:
syms R
X = 3;
h1 = .5 - [.25 - (1/4*(R^2))*((R^2)-.0625)]^(1/2) == 5;
solve(h1,R)
However, when I try to solve h1 when it equals any value other than zero, I get the error - Empty sym: 0-by-1. Can anyone explain to me why this is happening?

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回答（1 个）

Marco Riani
Marco Riani 2020-1-4
First of all it is necessary to replace [ ] with ( ) in your equation.
h1= .5 - (.25 - (1/4*(R^2))*((R^2)-.0625))^(1/2) == 5;
solve(h1,R)
Finally, If you try to plot your equation
x=-200:0.1:200;
y=.5 - (.25 - (1/4*(x.^2)).*((x.^2)-.0625)).^(1/2) -5;
plot(x,y)
you can see that y is never 0
Hope it helps
  1 个评论
Walter Roberson
Walter Roberson 2020-1-4
It is not necessary to replace the [] with (), but the code is more efficient if you do use ()

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