Any way to solve parametric inequations?
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09-14-2021, 09:35 AM
Post: #11
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RE: Any way to solve parametric inequations?
(09-14-2021 05:13 AM)jte Wrote:(09-13-2021 07:42 PM)Albert Chan Wrote: ⋮ Good catch ! Another bug report ... Perhaps it should be setup with 2 assumes (y≥0, y≤0), like ti-89 solution. Or, "safer" assumes (y>0, y<0), and handle y==0 edge case separately. Better yet, implement CAS do assume stuff automatically ! (09-13-2021 07:42 PM)Albert Chan Wrote: Or, for y≠0, reduce to simple inequality, with t = x/y Translate t = x/y back to (x,y) world ... First, edge case out of the way: if (y==0) then return (x!=0) (SIGN(x)!=SIGN(y)) AND (x!=-y) With SIGN(), we could remove test for edge case Unfortunately, CAS SIGN() have bugs (HOME side, SIGN() seems OK) CAS> SIGN([-1E-10, 0., 1E-10] → [-1., 0., -1.] CAS> SIGN([-1E-12, 0., 1E-12]) → [0., 0., 0.] CAS> SIGN(+inf) → 1 CAS> SIGN(1E400) → undef |
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