//To calculate the angle of acceptance
n1 = 1.563;    //refractive index of core
n2 = 1.498;    //refractive index of cladding
NA = sqrt(n1^2 - n2^2);      //numerical aperture 
alpha_i = asind(NA);        //angle of acceptance, degrees
deg = int(alpha_i);       //angle in degrees
t = 60*(alpha_i-deg);
mint = int(t);       //angle in minutes
printf("the angle of acceptance is %d degrees %d minutes",deg,mint);

//answer given in the book is wrong