error when using diff() on trigonometric functions

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alex pabouctsidis 2013-3-14

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https://ww2.mathworks.cn/matlabcentral/answers/67184-error-when-using-diff-on-trigonometric-functions

Hello,

When i try to apply this in matlab:

syms x
diff(cos(x))

I get :

ans =
diff(cos(x), x)

Instead of -sin(x) as expected. The examples and help show that it should work for trig functions and I don't understand why this isn't working for me.

Is this a kind of bug? Has anyone encountered this before?

Thanks, Alex

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Jan 2013-3-14

Did you create a variable or function called "cos" before?

alex pabouctsidis 2013-3-14

I had a syms cos(phi) for another variable, which in hindsight was a bit dumb :P

i removed it and it works now.

thanks!

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