aide svp exercice 2 en entier pour demain merci d'avance.

tan30° = BC/AB ⇒ BC = AB x tan30°

                                    = 11 x 0.577

                                    = 6.35 m

BC = 6.35 m

BT = BC + CT = 6.35 + 0.80 = 7.15 m

tan30° BT/RB ⇒RB = BT/tan30°

                                = 7.15/0.577 = 12.39 m

RB = RA + AB ⇒ RA = RB - AB

                                  = 12.39 - 11

                                  1.39 m ≈ 1.40 m

RA = 140 cm