Array indices must be positive integers or logical values

I'm trying to solve for the variable T, but MATLAB is returning

Array indices must be positive integers or logical values.

Error in untitled (line 23)

Temp = ((T - Te)./(Tb - Te) == ((cosh(B(L - x))) + (Hc)/((B.*k).* ...

Here is the code:

%Question 9

syms Temp solx T Tb Te L D P Ac k Hc B x;

%Variables

Tb = 200;

Te = 20;

L = 8 * .01;

D = 5 * .001;

%B variables

P = (pi * D);

Ac = (pi * D.^2)/4;

k = 200;

Hc = 200;

%B equation

B = (Hc * P)/(k * Ac);

%input variable

x = 2 * .01;

%Equation

Temp = ((T - Te)./(Tb - Te) == ((cosh(B(L - x))) + (Hc)/((B.*k).* ...

sinh(B(L - x))))./((cosh(B.*L) + (Hc))./((B*k).*sinh(B.*L))));

%solve

solx = solve(Temp, T);

How can I fix this error?

Answer 1

[Voss]

You probably mean

B.*(L - x)

instead of

B(L-x)

in two places.

[Justin]

Thanks!

Answer 2

[the cyclist]

I'm guessing that when you wrote

B(L - x)

(in two places), you intended this multiplication:

B.*(L - x)

instead. The way your wrote it, you are trying to index the (L-x)th element of B (which is why you got the error).

[Justin]

Thanks!