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C NUMERICAL METHODS: FORTRAN Programs, (c) John H. Mathews 1994
C To accompany the text:
C NUMERICAL METHODS for Mathematics, Science and Engineering, 2nd Ed, 1992
C Prentice Hall, Englewood Cliffs, New Jersey, 07632, U.S.A.
C This free software is complements of the author.
C
C Algorithm 7.1 (Composite Trapezoidal Rule).
C Section 7.2, Composite Trapezoidal and Simpson's Rule, Page 365
C
SUBROUTINE TRAPRU(F,A,B,M,Trule)
INTEGER K,M
DOUBLE PRECISION A,B,H,Sum,Trule,X
EXTERNAL F
H=(B-A)/M
Sum=0
DO K=1,M-1
X=A+H*K
Sum=Sum+F(X)
ENDDO
Sum=H*(F(A)+F(B)+2*Sum)/2
Trule=Sum
RETURN
END
SUBROUTINE XTRAPRU(F,A,B,M,Trule)
C This subroutine uses labeled DO loop(s).
INTEGER K,M
DOUBLE PRECISION A,B,H,Sum,Trule,X
EXTERNAL F
H=(B-A)/M
Sum=0
DO 10 K=1,M-1
X=A+H*K
Sum=Sum+F(X)
10 CONTINUE
Sum=H*(F(A)+F(B)+2*Sum)/2
Trule=Sum
RETURN
END
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