| 1 | c $Header$ |
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| 2 | SUBROUTINE coefpoly ( Xf1, Xf2, Xprim1, Xprim2, xtild1,xtild2 , |
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| 3 | , a0,a1,a2,a3 ) |
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| 4 | IMPLICIT NONE |
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| 5 | c |
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| 6 | c ... Auteur : P. Le Van ... |
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| 7 | c |
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| 8 | c |
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| 9 | c Calcul des coefficients a0, a1, a2, a3 du polynome de degre 3 qui |
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| 10 | c satisfait aux 4 equations suivantes : |
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| 11 | |
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| 12 | c a0 + a1*xtild1 + a2*xtild1*xtild1 + a3*xtild1*xtild1*xtild1 = Xf1 |
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| 13 | c a0 + a1*xtild2 + a2*xtild2*xtild2 + a3*xtild2*xtild2*xtild2 = Xf2 |
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| 14 | c a1 + 2.*a2*xtild1 + 3.*a3*xtild1*xtild1 = Xprim1 |
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| 15 | c a1 + 2.*a2*xtild2 + 3.*a3*xtild2*xtild2 = Xprim2 |
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| 16 | |
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| 17 | c On en revient a resoudre un systeme de 4 equat.a 4 inconnues a0,a1,a2,a3 |
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| 18 | |
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| 19 | REAL*8 Xf1, Xf2,Xprim1,Xprim2, xtild1,xtild2, xi |
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| 20 | REAL*8 Xfout, Xprim |
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| 21 | REAL*8 a1,a2,a3,a0, xtil1car, xtil2car,derr,x1x2car |
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| 22 | |
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| 23 | xtil1car = xtild1 * xtild1 |
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| 24 | xtil2car = xtild2 * xtild2 |
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| 25 | |
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| 26 | derr= 2. *(Xf2-Xf1)/( xtild1-xtild2) |
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| 27 | |
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| 28 | x1x2car = ( xtild1-xtild2)*(xtild1-xtild2) |
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| 29 | |
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| 30 | a3 = (derr + Xprim1+Xprim2 )/x1x2car |
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| 31 | a2 = ( Xprim1 - Xprim2 + 3.* a3 * ( xtil2car-xtil1car ) ) / |
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| 32 | / ( 2.* ( xtild1 - xtild2 ) ) |
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| 33 | |
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| 34 | a1 = Xprim1 -3.* a3 * xtil1car -2.* a2 * xtild1 |
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| 35 | a0 = Xf1 - a3 * xtild1* xtil1car -a2 * xtil1car - a1 *xtild1 |
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| 36 | |
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| 37 | RETURN |
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| 38 | END |
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