bonjour
la somme des angles d'un triangle = 180 °
180 - ( x + 3 x ) = 180 - 4 x
180 - 4 x = 90
- 4 x = 90 - 180
- 4 x = - 90
x = 22.5
ABC = 22.5 °
ACB = 3 * 22.5 = 67.5 °
BAC = 90 °
bon dimanche
