I'm trying to simplify an expression or equation symbolically and I get the same error every time. Undefined function or variable 'x'.

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MichaelTee 2016-2-6

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评论： Walter Roberson 2021-5-25

采纳的回答： Meghana Dinesh

I'm trying to simplify an expression symbolically and I get the same error every time.

Undefined function or variable 'x'.

I'm even using the actual example matlab provides. Trying to just simplify the expression sin(x)^2 + cos(x)^2 I get the error everytime. I'm brand new...what am I missing.

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Meghana Dinesh 2016-2-6

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编辑：Meghana Dinesh 2016-2-6

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What exactly is your command? It seems like you haven't told MATLAB what the value of x is. First, initialize a value for x and the carry on.

 x = 0.5;
 sin(x)^2 + cos(x)^2;

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MichaelTee 2016-2-6

I tried your code and it gives me a specific answer. I want to simplify an expression. Not get a specific answer.

Walter Roberson 2016-2-6

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simplify() requires the Symbolic Toolbox, and it works on symbolic expressions.

syms x
simplify( sin(x)^2 + cos(x)^2 )

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Bala Abhirami 2021-5-25

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编辑：Bala Abhirami 2021-5-25

The function u[1]/(u[2]^0.5) shows the error "result of the function is undefined" in matlab simulink user defined function. What could be the reason?

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Walter Roberson 2021-5-25

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Simulink uses MATLAB indexing syntax, so you need () instead of []

u(1)/(u(2)^0.5)

You might be able to use

u(1)/sqrt(u(2))

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