Infinite or Not-a-Number function value encountered.

Originally I tried to calculate

int(int((sin(q*A*sin(phi)/2)*sin(q*B*sin(phi)/2)*4/(q^2*A*B*sin(phi)*cos(phi)))^2*sin(q*C*cos(theta)/2)*2/(C*q))^2*sin(theta),theta,0,pi/2),phi,0.pi/2)

however MATLAB fail to show proper equation. So I change to use 'quad' function instead of 'int'

I just put A=B=C=7 and q=0.1 and tried to calculate...but failed. How can I calculate this equation?

-(183750365601059840*sin((7/20*sin(phi))).^4)./(8477503880968187*sin(phi).^2.*(sin(phi).^2. - 1) --> this equation comes from int((sin(q*A*sin(phi)/2)*sin(q*B*sin(phi)/2)*4/(q^2*A*B*sin(phi)*cos(phi)))^2*(sin(q*C*cos(theta)/2)*2/(C*q))^2*sin(theta),theta,0,pi/2) and put A, B, C, q values.

------------------------------------------------------------------------------------------

quad(@(phi) -(183750365601059840*sin((7/20*sin(phi))).^4)./(8477503880968187*sin(phi).^2.*(sin(phi).^2. - 1)),0.0001,pi/2)

Warning: Infinite or Not-a-Number function value encountered.

> In quad at 109

ans =

   NaN

Answer 1

[David Sanchez]

Besides the parenthesis unbalanced, you are dividing by zero.

for phi = pi/2

(8477503880968187*sin(phi)).^2.*(sin(phi).^2. - 1) = 0

Then:

r=-(183750365601059840*sin((7/20*sin(phi))).^4)/...
    (8477503880968187*sin(phi)).^2.*(sin(phi).^2. - 1)

will yield NaN.

[MinHyung]

Thank you very much!