From the top of a 150 m tall building A, the angle of elevation to the top of the building B is 45 degrees and the angle of depression to the bottom of the building B is 30 degrees. What is the height of the building B?
From the top of a 150 m tall building A, the angle of elevation to the top of the building B is 45 degrees and the angle of depression to the bottom of the building B is 30 degrees. What is the height of the building B? Correct Answer 150 (1 + √3) m
Calculation:
From the given information the diagram can be drawn as
[ alt="F1 Mohd.S 22-07-2020 Savita D1" src="//storage.googleapis.com/tb-img/production/20/07/F1_Mohd.S_22-07-2020_Savita_D1.png" style="width: 163px; height: 249px;">
Let XY be the length of building A
PQ be the length of building B
XP = YR
In ΔXYP
tan 30° = XY/XP
1/√3 = 150/XP
⇒ XP = 150√3 m
Now,
In Δ QYR
tan 45° = QR/YR
1 = QR/150√3
⇒ QR = 150√3
∴ Height of building B
⇒ PQ = QR + PR = 150 + 150√3
⇒ PQ = 150 (√3 + 1)
মোঃ আরিফুল ইসলাম
Feb 20, 2025