- #1
intervoxel
- 195
- 1
I want to convert a recursive real formula to rational number representation, but I get the wrong response.
For the real formula:
k = 1.9903694533443939
u1 = -12.485780609032208
u2 = -6.273096981091879
u3 = k * u2 -u1
/// 1st iteration
u3 = -1.7763568394002505E-15 // approx. zero
/// 2nd iteration
u3 = 6.273096981091875
/// 3rd iteration
u3 = 12.485780609032204
which are the correct values
For the rationalized formula we have
kn=39270881, kd=19730448
u1n=-234750193, u1d = 18801403
u2n=-181086902, u2d=28867225
u3n = u1d * u2n * kn - u1n * u2d * kd;
u3d = u1d * u2d * kd;
/// 1st iteration
u3n = -21418193, u3d = -4484756162545334248
u3n/u3d = -3.552713678800501E-15 // approx. 0, ok
/// 2nd iteration
u3n = -417378632937067183, u3d = -909312338189447552
u3n/u3d = 6.273096981101384 // ok
/// 3rd iteration
u3n = -366571621992223341, u3d = 216113855164233728
u3n/u3d = 0.913588924930172 // wrong!
Can anyone figure out what's wrong?
Thank you in advance.
For the real formula:
k = 1.9903694533443939
u1 = -12.485780609032208
u2 = -6.273096981091879
u3 = k * u2 -u1
/// 1st iteration
u3 = -1.7763568394002505E-15 // approx. zero
/// 2nd iteration
u3 = 6.273096981091875
/// 3rd iteration
u3 = 12.485780609032204
which are the correct values
For the rationalized formula we have
kn=39270881, kd=19730448
u1n=-234750193, u1d = 18801403
u2n=-181086902, u2d=28867225
u3n = u1d * u2n * kn - u1n * u2d * kd;
u3d = u1d * u2d * kd;
/// 1st iteration
u3n = -21418193, u3d = -4484756162545334248
u3n/u3d = -3.552713678800501E-15 // approx. 0, ok
/// 2nd iteration
u3n = -417378632937067183, u3d = -909312338189447552
u3n/u3d = 6.273096981101384 // ok
/// 3rd iteration
u3n = -366571621992223341, u3d = 216113855164233728
u3n/u3d = 0.913588924930172 // wrong!
Can anyone figure out what's wrong?
Thank you in advance.