//Ex:3.17
clc;
clear;
close;
n=10;// number of isotropic elements
// d=y/4
// Do=4n*(d/y)
// Do=4n*(y/4y)=2n(1/4)
Do=4*n*(1/4);
D0=10*log(Do)/log(10);// Directivity in db
printf("the Directivity = %d dB", D0);