Euclid: The ElementsGrade 8dialectic Stage

Pons Asinorum

Proposition V proves that the base angles of an isosceles triangle are equal. Called "Pons Asinorum" (the Bridge of Asses), this proof has been considered a test of mathematical ability since medieval times. The proof is more complex than Proposition I, requiring the construction of auxiliary points and the comparison of multiple pairs of congruent triangles.

The Text

What You'll Learn

1

Comprehension

States what the theorem claims: base angles of isosceles triangle are equal

2

Cause & Consequence

Explains why the auxiliary points F and G are needed

3

Meaning

Reflects on why this proof is called "Bridge of Asses" - a test of ability

4

Evidence

Points to a specific step or pair of triangles in the proof

5

Defense

Maintains or thoughtfully revises their position under challenge

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  • 1.Read the text carefully
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