File: INTEGR.V2 of Tape: Various/Decus/decus-3

(Source file text) 

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PROGRAM INTEGRATION(INPUT,OUTPUT);

    VAR ANFANG,ENDE,FLAECHE: REAL;


(*************** HIER INTEGRAND DEFINIEREN ******************)
    FUNCTION F(X: REAL): REAL;
        BEGIN
            F := SIN(X)
        END;
(************************************************************)



    FUNCTION INTEGRAL(A,B: REAL): REAL;

        CONST   EPSILON = 1E-8;
        VAR     K,N,I,J: INTEGER;
                DELTA,SUMME,LETZTWERT: REAL;
                ROMBERG: ARRAY[0..12] OF REAL;

    BEGIN
        K := 0;  N := 1;  DELTA := B-A;
        ROMBERG[0] := ( F(A) + F(B) )*DELTA/2;

        REPEAT
            LETZTWERT := ROMBERG[0];
            K := K+1;  N := 2*N;  DELTA := DELTA/2;
            SUMME := 0;
            FOR J := 1 TO N DIV 2 DO
                SUMME := SUMME + F(A + (2*J-1)*DELTA);
            ROMBERG[K] := ROMBERG[K-1]/2 + SUMME*DELTA;
            I := 1;
            FOR J := K-1 DOWNTO 0 DO
                BEGIN   I := 4*I;
                    ROMBERG[J] := (I*ROMBERG[J+1] - ROMBERG[J])/(I-1)
                END
        UNTIL ABS(ROMBERG[0]-LETZTWERT)<ABS(ROMBERG[0]*EPSILON);

        INTEGRAL := ROMBERG[0]
    END (* INTEGRAL *);


BEGIN
    WRITELN("B E S T I M M T E S   I N T E G R A L");
    WRITELN;
    WRITE("INTERVALLGRENZEN: ");  READ(ANFANG,ENDE);
    FLAECHE := INTEGRAL(ANFANG,ENDE);
    WRITELN;
    WRITELN("WERT DES INTEGRALS: ", FLAECHE :20:10)
END.

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