"Inner matrix dimensions must agree"

Hi all,

I know this is simple, but I still can't see the solution. I'm trying to plot a function which uses the 4th power of sinh and cosh. I can't figure out how to communicate it to MATLAB properly, so

k = 1.3 * 10^(-23);
T1 = 100;
T2 = 200;
T3 = 300;

j = 0:10:500;

lambda = 2* cosh(j) * (1 + 2 * sqrt(4 * sinh(j) * sinh(j) * sinh(j) * sinh(j) +1) );
F1 = k * T1 * log(lambda);
F2 = k * T2 * log(lambda);
F3 = k * T3 * log(lambda);

plot(j, F1(j), j, F2(j), j, F3(j))
hleg1 = legend('at 100 K', 'at 200 K', 'at 300 K');

results in

Error using  * 
Inner matrix dimensions must agree.

Error in Energy (line 8)
lambda = 2* cosh(j) * (1 + 2 * sqrt(4 * sinh(j) * sinh(j) * sinh(j) *
sinh(j) +1) );

Could anyone tell me how to reformulate line 8?

Thanks!

Answer 1

[Walter Roberson]

Change

sqrt(4 * sinh(j) * sinh(j) * sinh(j) * sinh(j) +1)

to

sqrt(4 * sinh(j).^4 + 1)

[Nina]

Thank you! Unfortunately, I'm still getting the same error message. Do you know any alternative solution?

[ChristianW]

... cosh(j) .* (1 + ...

and

plot(j, F1, j, F2, j, F3)

[Nina]

Yes, that solved it! Thank you very much, Christian!