bonjour
1. FA² = FG² + GA²
5² = 3 ² + 4 ²
25 = 9 + 16
25 = 25 ⇔ FAG est rectangle en G
2. AF/AD = AG/AE = FG/DE
5/AD = 4/10.8 ⇔ AD = 13.5 cm
3. FD = AD - AF = 13.5 - 5 = 8.5 cm
4. AF/ AB = AG/AC = FG/BC
4 /6.25 = 3 / BC
BC = 4.6875
4 * 4.6875 = 18 .75
6.25 * 3 = 18.75
Les rapports de Thalès sont égaux donc ( FG) // (BC)
