Thales' Theorem

📘 Definition

Thales' Theorem

Let ABC be a triangle and D and E two points, with D on line (AB) and E on line (AC), such that line (DE) is parallel to line (BC).

AD / AB = AE / AC = DE / BC

Converse of Thales' Theorem

In triangle ABC, if D belongs to [AB] and E belongs to [AC], and if AD/AB and AE/AC are equal, then lines (DE) and (BC) are parallel.

🧠 Formula

✏ Example

2 / 4 = 2 / 4 = 3 / 6