Cyrene and Athens · c. 465-c. 398 BCE
Theodorus of Cyrene
Theodorus of Cyrene was Greek mathematician and teacher. He is remembered for demonstrations concerning irrational square roots.
Surviving evidence supports the broad historical connection, but details of authorship, dates, or attribution are incomplete and are presented cautiously.
3-5, 6-8, 9-12, College
The person and the work
Biography
Theodorus of Cyrene was Greek mathematician and teacher associated with Cyrene and Athens. He is remembered for demonstrations concerning irrational square roots.
Plato’s Theaetetus preserves the setting of his lesson on square roots from three through seventeen. Together, these contributions connect number sense, algebra and functions, and geometry and measurement to the working problems, tools, and questions of the period.
Mathematical contribution
What this hero added or preserved
Core mathematical work
He is remembered for demonstrations concerning irrational square roots.
Method, teaching, or application
Plato’s Theaetetus preserves the setting of his lesson on square roots from three through seventeen.
Why this matters
The larger lesson
Theodorus of Cyrene shows that mathematics grows through proof, calculation, observation, design, teaching, or careful records. The lasting lesson is that number sense, algebra and functions, and geometry and measurement can turn a difficult question into a method another person can inspect and reuse.
Place the work in time
Timeline
- c. 465
Life and working period
Theodorus of Cyrene worked as Greek mathematician and teacher in Cyrene and Athens.
- Legacy
Lasting mathematical connection
Plato’s Theaetetus preserves the setting of his lesson on square roots from three through seventeen.
Key idea
Numbers reveal structure
Theodorus of Cyrene’s story shows that numbers are not only labels. They can be classified, compared, decomposed, and arranged to reveal patterns.
When 311 is divided by 6, the quotient is 51 with remainder 5. That remainder is structural information, not a mistake.
Try it yourself
Find the quotient and remainder
Divide 311 by 6. State the quotient and remainder.
- Estimate how many full groups fit.
- Multiply the divisor by the quotient.
- Subtract to find the remainder.
Show the answer
311 = 6 × 51 + 5, so the quotient is 51 and the remainder is 5.
Math at work
Scientists and astronomers use the same habits
Scientists and astronomers use number sense to plan, compare, test, or communicate decisions. Theodorus of Cyrene’s work provides a historical example of that connection.
Keep curiosity alive
A little-known fact
Plato’s Theaetetus preserves the setting of his lesson on square roots from three through seventeen.
Every detail commonly associated with Theodorus of Cyrene is documented with modern certainty.
The broad contribution is historically important, while dates, authorship, and later attribution require careful labels.
Keep exploring
Connected learning paths
Related math terms
- Place value
- Prime number
- Number pattern
- Variable
Practice these ideas
- AdditionPractice adding whole numbers, integers, and decimals.
- SubtractionPractice subtracting whole numbers, including results below zero.
- Pre-AlgebraBridge arithmetic and algebra with integers, ratios, and equations.
- Algebra IPractice equations, variables, functions, ratios, and inequalities.
- Algebra IIWork with quadratics, polynomials, systems, and sequences.