//Example 27.8
//Let I_0 be the initial intensity.
//Reduced intensity I=0.1*I_0, as intensity is reduced by 90%
//Using I=I_0*(cosd(theta))^2 and substituting value for I,we get
theta=acosd(sqrt(0.1));//Angle;
printf('Angle required = %0.1f deg',theta)
//Openstax - College Physics
//Download for free at http://cnx.org/content/col11406/latest