Can you tell us what the values of a, b, k, t, and epsilon are? Then just take it one term at a time. And there is an ambiguity around x because of missing parentheses. Can you tell us if x is inside the sine argument, or between the sin and cos terms?
a = 2;
b = 1;
c = 1;
k = 1;
t = 1;
epsilon = 1;
x = linspace(0, 5*pi, 1000);
for index = 1 : numel(x)
thisx = x(index);
term1 = (2 * epsilon * a^2) / (pi^2 * b * (a - b));
term2 = sin(pi * k * b / a) / k^2;
term3 = sin(pi * k * thisx / a); % Does x really go here like this???
term4 = cos(pi * k * c * t / a);
f(index) = term1 * sum(term1 .* term2 .* term3);
end
plot(x, f, 'b-', 'LineWidth', 2)
grid on
xlabel('x');
ylabel('f');
