Réponses

2013-03-22T17:57:27+01:00

DCB = 30° tan 30° = DB/4 => DB = 4tan30° = 4V3/3

triangle ADB rectangle

DBC = 60 => ADB = 30° et DAB = 60°

triangel EDC: tan60° = ED/5 => ED = 5V3

EC² = 75 + 25 = 100 => EC = 10

Aire EDC =2,5.5V3 = 12,5.V3