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Question 2975: Membership in a Circle Boundary

On this page
  1. Original question and givens
  2. Definition and scope
  3. Step-by-step derivation
  4. Reverse checks
  5. Result
  6. This question review and source binding

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R0004-02975 · q-20261005-advance-20261006-r05-circle-0025

Original question and givens

Use one equal-unit orthonormal Euclidean Cartesian frame. The circle boundary has center O=(12, -19) and radius r=23≥0. For P=(35, -19), is P a member of the circle boundary, not merely of the filled disk?

  • G001 — Use one equal-unit orthonormal Euclidean Cartesian frame. The circle boundary has center O=(12, -19) and radius r=23≥0. For P=(35, -19), is P a member of the circle boundary, not merely of the filled disk?

Definition and scope

Use the original question domain, assumptions and cited MKO definitions. This item has second-context mathematical and bilingual review, with the model, answer and every arithmetic step independently recomputed from the original parameters; the source question remains a candidate.

Step-by-step derivation

S001 · implies

Before

orthonormal equal-length units;r=23≥0

After

C={P:distance(P,O)=r} is a boundary,not a filled disk

Conditions: none

The circle is the boundary at distance exactly r from the center,not the filled disk.For r=0 use the degenerate singleton{O},with no inside points and diameter length0.

Step identifiers and dependencies

Rule: circle_boundary_convention · Uses: G001

S002 · calculation

Before

radius squared := square(23)

After

radius squared = 529

Conditions: none

The square of the nonnegative radius is the distance-comparison threshold.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · calculation

Before

coordinate difference0 := sub(35, 12)

After

coordinate difference0 = 23

Conditions: none

Subtract the center coordinate from the point coordinate;do not square absolute coordinates instead.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

coordinate square0 := square(23)

After

coordinate square0 = 529

Conditions: none

Square this coordinate difference;a negative difference still contributes a nonnegative square.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · calculation

Before

coordinate difference1 := sub(-19, -19)

After

coordinate difference1 = 0

Conditions: none

Subtract the center coordinate from the point coordinate;do not square absolute coordinates instead.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · calculation

Before

coordinate square1 := square(0)

After

coordinate square1 = 0

Conditions: none

Square this coordinate difference;a negative difference still contributes a nonnegative square.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S005

S007 · calculation

Before

squared distance := sum(529, 0)

After

squared distance = 529

Conditions: none

In an orthonormal equal-unit frame,the Pythagorean relation adds the squared differences.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S006

S008 · implies

Before

d²=529;r²=529

After

requested classification=Yes

Conditions: none

Distance and radius are nonnegative,so squaring preserves their order.Equality means boundary,strictly smaller means inside,and larger means outside.No rounded square root is needed.

Step identifiers and dependencies

Rule: nonnegative_squared_distance_comparison · Uses: G001, S007

Reverse checks

  • S008 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S007 · premise_and_result_audit — Recompute squared distance with exact rational arithmetic, not rounded decimals.
  • S006 · premise_and_result_audit — Recompute coordinate square1 with exact rational arithmetic, not rounded decimals.
  • S005 · premise_and_result_audit — Recompute coordinate difference1 with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Recompute coordinate square0 with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute coordinate difference0 with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Recompute radius squared with exact rational arithmetic, not rounded decimals.
  • S001 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.

Result

Yes

The full substitutions and premise checks give the original answer; source identity,format and status are unchanged.

This question review and source binding

Review date: 2026-10-26

Original questions, answers, step expressions, numeric ASTs and historical records are retained. Source candidate labels remain historical and are not overwritten as formal proof.

Source hashes and review receipts
  • input commit: 0f7be61e2c22317a4075561dc822c87d881a50db
  • original question SHA-256: 330178faaf1253448f2bbd2b614dbc7e962d1968c46b7c1fa9053f180ff8031c
  • candidate record SHA-256: 551be1ec258efb239adb3393ecea2d56c6012e7b90df3437a7c63e4799b25cff
  • semantic review receipt SHA-256: 312ae86315346b8955842a547cb2d09246e1f826755f72c2a51f042e5c7d5c56
  • question-first witness SHA-256: 831f449ed41ff9144a290e534aa32adf7252d15b81c16ed5886a7dfd65dee70c
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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