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Question 28289: Principal Square Root of a Perfect Square

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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R0055-28289 · q-20261003-r01-power-root-0064

Original question and givens

Using the principal square root on the nonnegative reals, find the exact nonnegative value of √169.

  • G001 — Using the principal square root on the nonnegative reals, find the exact nonnegative value of √169.

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

source roles = [qf-principal-square-root-exact, principal_sqrt]

After

derived = [[single_nonnegative_exact_integer_root]]

Conditions: none

List this scalar/label/set/point answer role or mode-specific ordered fields,not an imposed universal tuple.Retain legacy domain/underscore operation and integer fractions with/1;original bilingual snapshots stay unchanged.

Step identifiers and dependencies

Rule: source_answer_roles_or_ordered_fields_without_JS · Uses: G001

S002 · calculation

Before

Legacy principal ORIGINAL radicand exact midpoint square0 := mul(85, 85)

After

Legacy principal ORIGINAL radicand exact midpoint square0 = 7225

Conditions: none

Substitute original roles exactly,without floating approximation or changed operands;extra teaching identities add no source-domain restrictions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · implies

Before

source roles = [Legacy principal ORIGINAL radicand, 169, 0, [0, 170], 85]

After

derived = [7225, No, 0, 85]

Conditions: none

Squaring is monotone on nonnegative integers;maintain low²<=n<high².The midpoint is BigInt floor((low+high)/2),not floating sqrt,and strictly shrinks the integer bracket.Derived values do not inherit SAFE bounds.

Step identifiers and dependencies

Rule: Legacy_isqrt_EACH_BigInt_integer_midpoint_bracket · Uses: G001, S002

S004 · calculation

Before

Legacy principal ORIGINAL radicand exact midpoint square1 := mul(42, 42)

After

Legacy principal ORIGINAL radicand exact midpoint square1 = 1764

Conditions: none

Substitute original roles exactly,without floating approximation or changed operands;extra teaching identities add no source-domain restrictions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · implies

Before

source roles = [Legacy principal ORIGINAL radicand, 169, 1, [0, 85], 42]

After

derived = [1764, No, 0, 42]

Conditions: none

Squaring is monotone on nonnegative integers;maintain low²<=n<high².The midpoint is BigInt floor((low+high)/2),not floating sqrt,and strictly shrinks the integer bracket.Derived values do not inherit SAFE bounds.

Step identifiers and dependencies

Rule: Legacy_isqrt_EACH_BigInt_integer_midpoint_bracket · Uses: G001, S004

S006 · calculation

Before

Legacy principal ORIGINAL radicand exact midpoint square2 := mul(21, 21)

After

Legacy principal ORIGINAL radicand exact midpoint square2 = 441

Conditions: none

Substitute original roles exactly,without floating approximation or changed operands;extra teaching identities add no source-domain restrictions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S005

S007 · implies

Before

source roles = [Legacy principal ORIGINAL radicand, 169, 2, [0, 42], 21]

After

derived = [441, No, 0, 21]

Conditions: none

Squaring is monotone on nonnegative integers;maintain low²<=n<high².The midpoint is BigInt floor((low+high)/2),not floating sqrt,and strictly shrinks the integer bracket.Derived values do not inherit SAFE bounds.

Step identifiers and dependencies

Rule: Legacy_isqrt_EACH_BigInt_integer_midpoint_bracket · Uses: G001, S006

S008 · calculation

Before

Legacy principal ORIGINAL radicand exact midpoint square3 := mul(10, 10)

After

Legacy principal ORIGINAL radicand exact midpoint square3 = 100

Conditions: none

Substitute original roles exactly,without floating approximation or changed operands;extra teaching identities add no source-domain restrictions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S007

S009 · implies

Before

source roles = [Legacy principal ORIGINAL radicand, 169, 3, [0, 21], 10]

After

derived = [100, Yes, 10, 21]

Conditions: none

Squaring is monotone on nonnegative integers;maintain low²<=n<high².The midpoint is BigInt floor((low+high)/2),not floating sqrt,and strictly shrinks the integer bracket.Derived values do not inherit SAFE bounds.

Step identifiers and dependencies

Rule: Legacy_isqrt_EACH_BigInt_integer_midpoint_bracket · Uses: G001, S008

S010 · calculation

Before

Legacy principal ORIGINAL radicand exact midpoint square4 := mul(15, 15)

After

Legacy principal ORIGINAL radicand exact midpoint square4 = 225

Conditions: none

Substitute original roles exactly,without floating approximation or changed operands;extra teaching identities add no source-domain restrictions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S009

S011 · implies

Before

source roles = [Legacy principal ORIGINAL radicand, 169, 4, [10, 21], 15]

After

derived = [225, No, 10, 15]

Conditions: none

Squaring is monotone on nonnegative integers;maintain low²<=n<high².The midpoint is BigInt floor((low+high)/2),not floating sqrt,and strictly shrinks the integer bracket.Derived values do not inherit SAFE bounds.

Step identifiers and dependencies

Rule: Legacy_isqrt_EACH_BigInt_integer_midpoint_bracket · Uses: G001, S010

S012 · calculation

Before

Legacy principal ORIGINAL radicand exact midpoint square5 := mul(12, 12)

After

Legacy principal ORIGINAL radicand exact midpoint square5 = 144

Conditions: none

Substitute original roles exactly,without floating approximation or changed operands;extra teaching identities add no source-domain restrictions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S011

S013 · implies

Before

source roles = [Legacy principal ORIGINAL radicand, 169, 5, [10, 15], 12]

After

derived = [144, Yes, 12, 15]

Conditions: none

Squaring is monotone on nonnegative integers;maintain low²<=n<high².The midpoint is BigInt floor((low+high)/2),not floating sqrt,and strictly shrinks the integer bracket.Derived values do not inherit SAFE bounds.

Step identifiers and dependencies

Rule: Legacy_isqrt_EACH_BigInt_integer_midpoint_bracket · Uses: G001, S012

S014 · calculation

Before

Legacy principal ORIGINAL radicand exact midpoint square6 := mul(13, 13)

After

Legacy principal ORIGINAL radicand exact midpoint square6 = 169

Conditions: none

Substitute original roles exactly,without floating approximation or changed operands;extra teaching identities add no source-domain restrictions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S013

S015 · implies

Before

source roles = [Legacy principal ORIGINAL radicand, 169, 6, [12, 15], 13]

After

derived = [169, Yes, 13, 15]

Conditions: none

Squaring is monotone on nonnegative integers;maintain low²<=n<high².The midpoint is BigInt floor((low+high)/2),not floating sqrt,and strictly shrinks the integer bracket.Derived values do not inherit SAFE bounds.

Step identifiers and dependencies

Rule: Legacy_isqrt_EACH_BigInt_integer_midpoint_bracket · Uses: G001, S014

S016 · calculation

Before

Legacy principal ORIGINAL radicand exact midpoint square7 := mul(14, 14)

After

Legacy principal ORIGINAL radicand exact midpoint square7 = 196

Conditions: none

Substitute original roles exactly,without floating approximation or changed operands;extra teaching identities add no source-domain restrictions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S015

S017 · implies

Before

source roles = [Legacy principal ORIGINAL radicand, 169, 7, [13, 15], 14]

After

derived = [196, No, 13, 14]

Conditions: none

Squaring is monotone on nonnegative integers;maintain low²<=n<high².The midpoint is BigInt floor((low+high)/2),not floating sqrt,and strictly shrinks the integer bracket.Derived values do not inherit SAFE bounds.

Step identifiers and dependencies

Rule: Legacy_isqrt_EACH_BigInt_integer_midpoint_bracket · Uses: G001, S016

S018 · calculation

Before

Legacy principal ORIGINAL radicand terminal root square := mul(13, 13)

After

Legacy principal ORIGINAL radicand terminal root square = 169

Conditions: none

Substitute original roles exactly,without floating approximation or changed operands;extra teaching identities add no source-domain restrictions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S017

S019 · calculation

Before

Legacy principal ORIGINAL radicand terminal successor square := mul(14, 14)

After

Legacy principal ORIGINAL radicand terminal successor square = 196

Conditions: none

Substitute original roles exactly,without floating approximation or changed operands;extra teaching identities add no source-domain restrictions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S018

S020 · implies

Before

source roles = [Legacy principal ORIGINAL radicand, 169, 13, 14]

After

derived = [169, 196]

Conditions: none

Adjacent integer bounds certify floor sqrt=low;an exact root separately needs low²=n,and the principal root is the single nonnegative branch.

Step identifiers and dependencies

Rule: Legacy_isqrt_terminal_floor_and_single_nonnegative_branch · Uses: G001, S019

S021 · implies

Before

source roles = [169]

After

derived = [13, Yes]

Conditions: none

Check root²=r and root>=0.Monotonicity of nonnegative squaring gives uniqueness;two signed equation roots are not the principal-root value.

Step identifiers and dependencies

Rule: Legacy_PERFECT_square_exact_NONNEGATIVE_principal_root · Uses: G001, S020

Reverse checks

  • S021 · premise_and_result_audit — Reverse-check complete original data,operands and premises;finite checks,conditional reasoning,formal proof and publication authority remain distinct.
  • S020 · premise_and_result_audit — Reverse-check complete original data,operands and premises;finite checks,conditional reasoning,formal proof and publication authority remain distinct.
  • S019 · premise_and_result_audit — Recompute Legacy principal ORIGINAL radicand terminal successor square with exact rational arithmetic, not rounded decimals.
  • S018 · premise_and_result_audit — Recompute Legacy principal ORIGINAL radicand terminal root square with exact rational arithmetic, not rounded decimals.
  • S017 · premise_and_result_audit — Reverse-check complete original data,operands and premises;finite checks,conditional reasoning,formal proof and publication authority remain distinct.
  • S016 · premise_and_result_audit — Recompute Legacy principal ORIGINAL radicand exact midpoint square7 with exact rational arithmetic, not rounded decimals.
  • S015 · premise_and_result_audit — Reverse-check complete original data,operands and premises;finite checks,conditional reasoning,formal proof and publication authority remain distinct.
  • S014 · premise_and_result_audit — Recompute Legacy principal ORIGINAL radicand exact midpoint square6 with exact rational arithmetic, not rounded decimals.
  • S013 · premise_and_result_audit — Reverse-check complete original data,operands and premises;finite checks,conditional reasoning,formal proof and publication authority remain distinct.
  • S012 · premise_and_result_audit — Recompute Legacy principal ORIGINAL radicand exact midpoint square5 with exact rational arithmetic, not rounded decimals.
  • S011 · premise_and_result_audit — Reverse-check complete original data,operands and premises;finite checks,conditional reasoning,formal proof and publication authority remain distinct.
  • S010 · premise_and_result_audit — Recompute Legacy principal ORIGINAL radicand exact midpoint square4 with exact rational arithmetic, not rounded decimals.
  • S009 · premise_and_result_audit — Reverse-check complete original data,operands and premises;finite checks,conditional reasoning,formal proof and publication authority remain distinct.
  • S008 · premise_and_result_audit — Recompute Legacy principal ORIGINAL radicand exact midpoint square3 with exact rational arithmetic, not rounded decimals.
  • S007 · premise_and_result_audit — Reverse-check complete original data,operands and premises;finite checks,conditional reasoning,formal proof and publication authority remain distinct.
  • S006 · premise_and_result_audit — Recompute Legacy principal ORIGINAL radicand exact midpoint square2 with exact rational arithmetic, not rounded decimals.
  • S005 · premise_and_result_audit — Reverse-check complete original data,operands and premises;finite checks,conditional reasoning,formal proof and publication authority remain distinct.
  • S004 · premise_and_result_audit — Recompute Legacy principal ORIGINAL radicand exact midpoint square1 with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Reverse-check complete original data,operands and premises;finite checks,conditional reasoning,formal proof and publication authority remain distinct.
  • S002 · premise_and_result_audit — Recompute Legacy principal ORIGINAL radicand exact midpoint square0 with exact rational arithmetic, not rounded decimals.
  • S001 · premise_and_result_audit — Reverse-check complete original data,operands and premises;finite checks,conditional reasoning,formal proof and publication authority remain distinct.

Result

13

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: 8ebafb214c1e9afcbe1cbb6d855564e0cefe9b2396c9704423a732130d190f5a
  • candidate record SHA-256: 12346238cd826dd1ce4334d24365a3a15f1c184a94462da305ac14ba95a7111f
  • semantic review receipt SHA-256: 6af367dae24a584f3596525c4953bbc2115343efd68cc9083693eb5c1ef2e683
  • question-first witness SHA-256: 611eb69f3716404b968296a8b0d7d8c61b5ca18129d406f1ff9c7c11e10ffb4e
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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