Denominator is positive on the frustum
NOT A NOVELTY CLAIM. This is a machine-checked formalisation, decided by the Lean 4 kernel and depending on no axiom. It is dated and citable. Prior art, where it exists, is cited below. No discovery is claimed.
The projection never divides by zero on the declared frustum: the denominator stays positive for every depth between the near and far planes.
Proposition
∀ k ∈ [(-5 : Int), -4, -3, -2, -1, 0, 1, 2, 3, 4, 5], 0 < den kProof
By decide in three.lean. The kernel reduces the proposition and reports no axiom dependency.
Sources and identifiers
- Lean source · src/pair/formal/proofs/three.lean
- Typeset paper · src/research/lean-theorems.tex
- Repository deposit · doi:10.5281/zenodo.21787144
- Author · ORCID 0009-0000-7312-9778
- Deposit record ·
three--denominator_is_positive_on_the_frustum
Proved in the same file
- Closure is one hundred sixty two
- Closure is the product
- Closure has no duplicate
- Closure is complete
- Address inverts
- Addresses are the interval
- The compound fraction clears
- Focal plane is unit scale
- Depth is strictly monotone
- Frustum brackets the focal plane
- Reflection is an involution
- Reflection closes on the closure
- Reflection has no fixed point
- The closure is eighty one orbits
- Orbit positions cancel
- Reflection complements the address
- The involution laws are general