PROGRAM HASIDF DOUBLE PRECISION DFR,F,X,H F(X)=DSIN(X) H=1.0D-1 WRITE(*,*)'Give X : ' READ(*,*)X DO 100 I=1,10 DFR=(4*F(X+H)-F(X+H+H)-3*F(X))/H/2 WRITE(*,200)'H = ',H,'; 2nd Forward = ',DFR H=H/10 100 CONTINUE WRITE(*,300)'True value : ',DCOS(X) 200 FORMAT(1H ,A4,F13.10,A15,F22.16) 300 FORMAT(1H ,A13,F22.16) END