Solving equations in Matlab

I am trying to solve a transcendental equation in Matlab, as follows:

fAc=solve((QAc-1)/(QAc+1)==f*arccosh(exp(0.693/f)/2),f);

I am getting the error:

Undefined function or variable 'f'.

Error in analyz (line 74)
fAc=solve((QAc-1)/(QAc+1)==f*arccosh(exp(0.693/f)/2),f);

and I'm not sure how to fix it. I have given QAc fake values that are approximately what they will really be.

Adding a "syms fAc" gives the error:

Undefined function 'arccosh' for input arguments of type 'sym'.

If I try to solve it in Mathematica, I get a complex number (and I want to eventually take the absolute value of it if it ends up being complex).

I know that Mathematica solves this a lot easier, but I'm not sure how to use the "ToMatlab.m" package that I've seen people refer to.

Any help is appreciated.

Thanks.

[Walter Roberson]

Do you perhaps mean

syms f QAc

[Grant]

I get the same error if I try that.

Answer 1

[Azzi Abdelmalek]

It's not arccosh, It's acosh

[Grant]

I was using this as reference. I am using 2012a. Also, I get the same error if I change it to acosh.

[Azzi Abdelmalek]

syms QAc f 
fAc=solve((QAc-1)/(QAc+1)==f*acosh(exp(0.693/f)/2),f);

[Grant]

That works, thank you very much.

Would you mind giving a brief explanation as to why it does, as compared to what I was doing?

Thanks a lot.

EDIT: I just want to make sure, this will work if I give QAc a value right? or would I just remove QAc from the line "syms QAc f"?