Gougu theorem (Zhoubi suanjing)
Teorema gougu (Zhoubi suanjing)
- Date
- c. 100 BCE · confidence low
- Place
- Chang'an (Xi'an), Shaanxi, China
- Credited to
- Authors of the Zhoubi suanjing; proof by Zhao Shuang (3rd century)
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What was discovered
The Zhoubi suanjing states the relationship between the legs (gou and gu) and the hypotenuse and applies it to measuring distances to the Sun; Zhao Shuang added a proof by area dissection. It is an independent development of the Pythagorean theorem.
The dating of the Zhoubi is disputed (between the 4th and 1st centuries BCE). The result was already known to the Babylonians (Plimpton 322).
What it led to
- surveying and distance measurement by similar triangles
- right-triangle problems in the Nine Chapters