UR² = 27² + 125² = 16354
BE = V(125²+75²) = 25V(25+9) = 25V34
Thalès: IR/BE = 48/75 => IR = 25V34.16/25 =
LI/LB = 48/75 => LI = 125.48/75 = 80
BI = 125 - 80 = 45
UI² = 45² + 75²
IR² + UI² = 256.34 + 45² + 75² = 16354 = UR²
donc le triangle est rectangle