A=-5;
B=5;

x=linspace(A,B);

a=1;
y1=sin(a*x)./x;


a=3;
y2=sin(a*x)./x;

plot(x,y1,  x,y2)

legend('a=1',  'a=3' )


title('sin(ax)/x')

xlabel('x')

grid on