Integrand output size does not match the input size.

I'm giving theta ranging from 1 to 180 from excel file but it is showing this error.

theta = xlsread('orientations.xlsx',1,'A:A');
theta = theta * pi /180;


O = zeros(180,1);
count = 1;
for i= 1 : length(theta)
    O_temp = integral2(@(theta_,phi_) sin(theta(i)) , 0, pi, 0, pi);
    O = (O_temp)^-1;
    count = count + 1;  
end