//chapter19
//example19.12
//page424

It=8.93 // A
Ic=8 // A

// we know that (It/Ic)^2=1+m^2/2 so making m as subject we get
m=(2*((It/Ic)^2-1))^0.5

printf("modulation factor = %.3f or %.3f percent \n",m,m*100)