Argument to dynamic structure reference must evaluate to a valid field name.

I was asked to use fsole to solve a problem but i keep getting this message "Argument to dynamic structure reference must evaluate to a valid field name."

this is my code

function fsolveDemo
% x(1) = theta1, x(2) = theta2
% x0 is a starting guess of theta1 and theta2.
x0 = [0.1,0.1];                        % Make a starting guess at the solution
options=optimset('Display','iter');   % Option to display output
x = fsolve(@myfun,x0,options);  % Call solver
plot(x(1),x(2))
end

function F = myfun(x)
t=(0:0.1:4);  p1=8; p2=1+t; L1=5; L2=6;
% Rewrite the equation in the form F(x) = 0
F = [((x(1))-atan(p2./p1)+ asin(L2*sin(x(2))/sqrt.(p1.^2+p2.^2)));((x(2))- acos((p1^2+p2.^2-L1^2-L2^2)./(2*L1*L2)))];
end

please tell me whats wrong

[EDITED, Jan, please apply a proper code formatting - thanks]

[Jan]

Please copy the complete error message. It is not efficient to guess, which line causes the error.

[ggeneral]

Argument to dynamic structure reference must evaluate to a valid field name.

Error in G_Emiko_Project2_4>myfun (line 23) F = [x(1)-atan(p2./p1)+ asin((L2*sin(x(2)))/sqrt.(p1.^2+p2.^2));

Error in fsolve (line 217) fuser = feval(funfcn{3},x,varargin{:});

Error in G_Emiko_Project2_4 (line 12) x = fsolve(@myfun,x0,options) % Call solver

Caused by: Failure in initial user-supplied objective function evaluation. FSOLVE cannot continue.

Answer 1

[Jan]

In

sqrt.(p1.^2+p2.^2)

Matlab assumes, that "sqrt" is a struct and "(p1.^2+p2.^2)" is the field name. Remove the dot after "sqrt".

You can find the source of such problem using the debugger:

dbstop if error

Then run the code again until it stops at the error. Now evaluated the line piece by piece, until you find, which expression fails.

[ggeneral]

it didnt work