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+//CHAPTER 3- THREE-PHASE A.C. CIRCUITS
+//Example 11
+
+disp("CHAPTER 3");
+disp("EXAMPLE 11");
+
+//SOLUTION
+function power_sum=p1(phi);
+power_sum=20*cos(phi);                 //power_sum=p1+p2=20*cos(phi) and in KiloWatts
+endfunction;
+function power_diff=p2(phi);
+power_diff=(20*sin(phi))/sqrt(3);      //power_diff=p1-p2=(20*sin(phi))/sqrt(3) and in KiloWatts
+endfunction;
+
+//solution (a): when phi=0
+power_sum=20*cos(0);                   //eq(i)
+power_diff=(20*sin(0))/sqrt(3);        //eq(ii)
+//solving eq(i) and eq(ii) to get values of p1 and p2
+A=[1 1;1 -1];
+b=[power_sum;power_diff];
+x=inv(A)*b; 
+x1=x(1,:);                             //to access the 1st row of 2X1 matrix 
+x2=x(2,:);                             //to access the 2nd row of 2X1 matrix 
+disp("Solution (a)"); 
+disp(sprintf("P1 + P2 = %d kW",power_sum));
+disp(sprintf("P1 - P2 = %d kW",power_diff));
+disp(sprintf("The two wattmeter readings are %d kW and %d kW",x1,x2));
+
+//solution (b): when phi=30 or %pi/6 (lagging)
+power_sum=20*cos(%pi/6);
+power_diff=(20*sin(%pi/6))/sqrt(3);
+A=[1 1;1 -1];
+b=[power_sum;power_diff];
+x=inv(A)*b; 
+x1=x(1,:);
+x2=x(2,:);
+disp("Solution (b)");
+disp(sprintf("P1 + P2 = %f kW",power_sum));
+disp(sprintf("P1 - P2 = %f kW",power_diff));
+disp(sprintf("The two wattmeter readings are %f kW and %f kW",x1,x2));
+
+//solution (c): when phi=60 or %pi/3
+power_sum=20*cos(%pi/3);
+power_diff=(20*sin(-(%pi/3)))/sqrt(3); //leading
+A=[1 1;1 -1];
+b=[power_sum;power_diff];
+x=inv(A)*b; 
+x1=x(1,:);
+x2=x(2,:);
+disp("Solution (c)");
+disp(sprintf("P1 + P2 = %f kW",power_sum));
+disp(sprintf("P1 - P2 = %f kW",power_diff));
+disp(sprintf("The two wattmeter readings are %f kW and %f kW",x1,x2));
+
+//solution (d): when phi=90 or %pi/2
+power_sum=20*cos(%pi/2);
+power_diff=(20*sin(%pi/2))/sqrt(3);   //leading
+A=[1 1;1 -1];
+b=[power_sum;power_diff];
+x=inv(A)*b; 
+x1=x(1,:);
+x2=x(2,:);
+disp("Solution (d)");
+disp(sprintf("P1 + P2 = %f kW",power_sum));
+disp(sprintf("P1 - P2 = %f kW",power_diff));
+disp(sprintf("The two wattmeter readings are %f kW and %f kW",x1,x2));
+
+//END