i am geting error in this line why Error: File: dfdddd.m Line: 32 Column: 89 Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.

    % M-file: torque_speed_curve.m
% M-file create a plot of the torque-speed curve of the 
%   induction motor of Example 7-5. 

% First, initialize the values needed in this program.
r1 = 0.641;                 % Stator resistance
x1 = 1.106;                 % Stator reactance
r2 = 0.332;                 % Rotor resistance
x2 = 0.464;                 % Rotor reactance
xm = 26.3;                  % Magnetization branch reactance
v_phase = 460 / sqrt(3);    % Phase voltage
n_sync = 1800;              % Synchronous speed (r/min)
w_sync = 188.5;             % Synchronous speed (rad/s)

% Calculate the Thevenin voltage and impedance from Equations
% 7-41a and 7-43.
v_th = v_phase * ( xm / sqrt(r1^2 + (x1 + xm)^2) );
z_th = ((j*xm) * (r1 + j*x1)) / (r1 + j*(x1 + xm));
r_th = real(z_th);
x_th = imag(z_th);

% Now calculate the torque-speed characteristic for many
% slips between 0 and 1.  Note that the first slip value 
% is set to 0.001 instead of exactly 0 to avoid divide-
% by-zero problems.
s = (0:1:50) / 50;           % Slip
s(1) = 0.001;
nm = (1 - s) * n_sync;       % Mechanical speed

% Calculate torque for original rotor resistance
for ii = 1:51
   t_ind1(ii) =(3 * v_th^2 * r2)./((w_sync.*s(ii).*((r_th+(r2./s(ii)).^2 + (x_th+x2)^2));
end

% Calculate torque for doubled rotor resistance


% Plot the torque-speed curve
plot(nm,t_ind1,'Color','k','LineWidth',2.0);
hold on;
xlabel('\itn_{m}','Fontweight','Bold');
ylabel('\tau_{ind}','Fontweight','Bold');
title ('Induction Motor Torque-Speed Characteristic','Fontweight','Bold');
legend ('Original R_{2}','Doubled R_{2}');
grid on;
hold off;

Answer 1

[Walter Roberson]

   t_ind1(ii) =(3 * v_th^2 * r2)./((w_sync.*s(ii).*((r_th+(r2./s(ii)).^2 + (x_th+x2)^2));
         1  0  1               0  12         3  2  34     5     6  54      5       4  32

You have two more ( than you have )

[Bader Herzallah]

how i can fix this error cuz id understand it

[Steven Lord]

x = ((1+2)

This isn't valid MATLAB code because it has more left parentheses ( than right parentheses ).

Your code has the same type of problem except instead of having one extra ( it has two. You need to determine, based on what you're trying to compute, which two of the ( are unmatched and so need to be deleted or need extra ) symbols added to match them.

[Walter Roberson]

My guess would be

   t_ind1(ii) =(3 * v_th^2 * r2)./(w_sync.*s(ii).*((r_th+(r2./s(ii)).^2 + (x_th+x2)^2)));