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+//===========================================================================
+//chapter 7 example 21
+
+clc;
+clear all;
+
+//variable declaration
+R	= 10;	//resistance in Ω
+XL	= 10;	//reactance  in Ω
+VL	= 440;	//load voltage in V
+
+//calculations
+Z	= sqrt((R^2)+(XL^2));		//impedance of each choking coil in Ω
+VP	= VL/sqrt(3);		//phase voltage in V
+IP	= VP/Z;		//phase current in A
+IL	= IP;		//line current in A
+phi 	= atan(XL/R);	//phase angle in  °
+phi1       = phi*180/%pi;
+
+W1	= VL*IL*cos((30*%pi/180)-(phi1*%pi/180));		//wattmeter reading in W
+W2	= VL*IL*cos((30*%pi/180)+(phi1*%pi/180));		//wattmeter reading in W
+
+//result
+mprintf("line current = %3.2f A",IL);
+mprintf("\nwattmeter reading = %3.2f W",W1);
+mprintf("\nwattmeter reading = %3.2f W",W2);
+