Tan angle BDC = 18/87
donc : angle BDC = 11,689369175439.....
donc angle ADC = 38+11,689369175439..... ≈ 49,689369175439.....°
Tan angle ADC = AC/CD
donc : Tan 49,689369175439.....° = AC/87
donc : AC = Tan 49,689369175439.....° × 87 = 102,548300516308.....
AB = AC - BC
= 102,548300516308..... - 18
= 84,548300516308..... m
≈ 84,55 m
