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An introduction to Euclid


Index --- introduction --- definitions --- axioms and postulates --- propositions --- other

Definitions
Axioms and Postulates
Other
Propositions and Constructions
Interesting Propositions
4. Congruent triangles (1) side-angle-side
5. Isosceles triangle base angles are equal (Pons Asinorum)
8. Congruent triangles (2) three sides
15. Opposite angles are equal
18. In triangle, greater angle is opposite greater side
20. In triangle, sum of two sides greater than third
26. Congruent triangles (3) side and two angles
29. Parallel lines makes angles equal
32. Angles of a triangle add up to 180°
34. Parallelograms have the opposite sides and angles equal
36. Parallelograms on equal bases and between the same parallels are equal area
47. Pythagoras' theorem
Interesting Constructions
1. Construct an equilateral triangle on a given line
9. Bisect an angle
11. Construct a right angle at a point on a line
31. Construct a parallel line through a point