1 SUBROUTINE AREA1 (X,Y,AREA,NSUM) 2C 3C*** CALCULATES INCREMEMTAL AREA OF VERTICAL TAIL SHADOWED BY MACH LINE 4C 5 DIMENSION X(4),Y(4) 6 AREA2=0. 7 A=SQRT((X(2)-X(1))**2+(Y(2)-Y(1))**2) 8 B=SQRT((X(3)-X(2))**2+(Y(3)-Y(2))**2) 9 C=SQRT((X(1)-X(3))**2+(Y(1)-Y(3))**2) 10 S=(A+B+C)/2. 11 AREA=SQRT(S*(S-A)*(S-B)*(S-C)) 12 IF(NSUM.NE.4.AND.NSUM.NE.6) GO TO 40 13 A2=SQRT((X(4)-X(3))**2+(Y(4)-Y(3))**2) 14 B2=SQRT((X(1)-X(4))**2+(Y(1)-Y(4))**2) 15 S2=(A2+B2+C)/2. 16 AREA2=SQRT(S2*(S2-A2)*(S2-B2)*(S2-C)) 17 40 AREA=AREA+AREA2 18 RETURN 19 END 20