Why am I getting: "invalid syntax at "(" .A might be missing a closing ")"

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Jamie Al 2021-10-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1469341-why-am-i-getting-invalid-syntax-at-a-might-be-missing-a-closing

评论： Jamie Al 2021-10-8

What is messing here??

  source = ((-4*A^2*alpha)-(9*B^2*alpha))*(cos^2( (2*A) * XX).* sin^2( (3*B) * YY))...
      -( (5/2)*4*A^2*alpha+(5/2)*9*B^2*alpha)*(cos( (2*A) * XX).* sin( (3*B) * YY))...
       + ((4*A^2*alpha)*(sin^2((2*A) * XX).* sin^2( (3*B) * YY)))...
       + ((9*B^2*alpha)*(cos^2((2*A) * XX).* cos^2( (3*B) * YY))));
  

Error at first line where the cosine squared is

(cos^2( .. %underneath the paranthesis infront of cos^2

I don't understand???

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Stephen23 2021-10-8

编辑：Stephen23 2021-10-8

在 MATLAB Online 中打开

The functions COS and SIN require an input argument, so many of your function calls are invalid:

cos^2(..)  % invalid sytanx (COS has no input)
cos(..)^2  % valid syntax

I suspect that you actually want POWER .^ and not MPOWER ^

https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

Jamie Al 2021-10-8

I see!! Thanks!

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Answer 1

Walter Roberson 2021-10-8

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https://ww2.mathworks.cn/matlabcentral/answers/1469341-why-am-i-getting-invalid-syntax-at-a-might-be-missing-a-closing#answer_803971

In MATLAB, cos^2(x) and sin^2(x) are not valid operations. These will be interpreted as cos()^2(x) and sin()^2(x) which would involve invoking cos or sin with no parameters, and trying to raise the result to an expression that as 2 followed by an expression in () ... which would be intepreted as an invalid indexing operation since constants such as 2 cannot be indexed.

You need to instead code cos(x)^2 and sin(x)^2 .

... You should probably vectorize along the way.