Index exceeds the number of array elements (0).

prompt= 'Enter theta1 value';
A = input(prompt);
prompt = 'Enter phi1 value';
B = input(prompt);
prompt= 'Enter theta2 value';
A_ = input(prompt);
prompt = 'Enter phi2 value';
B_= input(prompt);

cos(C)= cos(A)*cos(A_)+ sin(A)*sin(A_)*cos(B-B_);
sin(C)= sqrt( 1- (cos(C))^2);

if A == (90)
    disp('2D random assembly')
    O= 1/180 ;
    J = integral2(@(A_,B_) O*sin(C)*sin(A_),0,180,0,180);
else 
    disp('3D random assemby')
    O= 1/360 ;
    J = integral2(@(A_,B_) O*sin(C)*sin(A_),0,180,0,180);
end

I am getting error(Index exceeds the number of array elements (0) ) in 10th line. Please explain why I am getting this error?

[KSSV]

cos(C)= cos(A)*cos(A_)+ sin(A)*sin(A_)*cos(B-B_);

The above line is not correct.

Answer 1

[VBBV]

%true
 prompt= 'Enter theta1 value';
A = input(prompt);
prompt = 'Enter phi1 value';
B = input(prompt);
prompt= 'Enter theta2 value';
A_ = input(prompt);
prompt = 'Enter phi2 value';
B_= input(prompt);
coC= cos(A)*cos(A_)+ sin(A)*sin(A_)*cos(B-B_);
siC= sqrt( 1- (coC.^2));
if A == (90)
  disp('2D random assembly')
  O= 1/180 ;
  J = integral2(@(A_,B_) O*siC.*sin(A_),0,180,0,180);
else 
  disp('3D random assemby')
  O= 1/360 ;
  J = integral2(@(A_,B_) O*siC.*sin(A_),0,180,0,180);
end

You are using parenthesis with undefined index on left side. Try above

[KSSV]

You have to consider the angle units in the above.... I don't understand why people are answering the same answer, once it answered.

Answer 2

[KSSV]

As you are expecting the angle to be in degrees, you have to use sind, cosd. If you enter the angles in radians, then use sin, cos.

You need to use like this:

prompt= 'Enter theta1 value';
A = input(prompt);
prompt = 'Enter phi1 value';
B = input(prompt);
prompt= 'Enter theta2 value';
A_ = input(prompt);
prompt = 'Enter phi2 value';
B_= input(prompt);

cosC= cosd(A)*cosd(A_)+ sind(A)*sind(A_)*cosd(B-B_);   % consider a different variable name cosC
sinC= sqrt( 1- (cosC)^2);   % consider a different variable name sinC 

if A == (90)
    disp('2D random assembly')
    O= 1/180 ;
    J = integral2(@(A_,B_) O*sinC*sind(A_),0,180,0,180);
else 
    disp('3D random assemby')
    O= 1/360 ;
    J = integral2(@(A_,B_) O*sinC*sind(A_),0,180,0,180);
end