[Trigonometry] HnD Type #4: Two Buildings-Two Angles made easy for SSC

In Aptitude by Support Staff

  1. Introduction: 2 Building 2 Angles
  2. Approach
  3. Mock Questions: 2 Building, 2 Angles

Introduction: 2 Building 2 Angles

Continuing in the series of “Trigonometry –>Height and Distance–> Five types of Questions.
4th type of question is “Two buildings and Two angles”. Here are example questions (both solved in the video)

  1. From the bottom of a 50m temple, the angle of elevation of the top of next building is 60. Similarly, from the bottom of the building, angle of elevation of the top of the temple is 30 degree. Find height of this building.
  2. From the top of a 90m cliff, angle of depression of top and bottom of a building are 30 and 60 degrees respectively. Find height of this building (SSC CGL 2012)

Approach

  • Since two angles are given, you make two equations of TAN using Topi-triangle shortcutTM.
  • Then combine the concept of rectangle (opposite sides have same length) And you’ll get the answer.
  • Check the following video to see how ^this approach exactly works. And after watching the video, solve the mock questions given at the bottom of this article.

If the video is not visible, check it directly on my youtube channel youtube.com/user/TheMrunalPatel

Mock Questions: 2 Building, 2 Angles

  1. From a 60 m tall building, the angle of depression of the top and the bottom of a tower is 30 and 60° respectively. Find the height of this tower.
  2. From the top half a 300 m high cliff,   the angles of depression of the bottom and top of a building are 60 and 30 respectively.  Find the height of this building
  3. watching from a window 40m  high of a multi-storey building, the angle of elevation of the top of a tower is found to be 45°. The angle of elevation of the top of the same tower from the bottom of this building is 60 degrees. Find height of tower
  4. from the top of a 60m tall building, the angle of depression of top and bottom of a tree are 30 and 60° respectively. 1) find the distance between building and tree.2)  find height of the tree. 3)  find the difference between the heights of trees and building.
  5. The top of two buildings of height 18m and 12m are connected by a cable. This cable makes an angle of 30 meter with the horizontal line passing from the top of the smaller building. Find length of the wire.
  6. The angle of elevation of top of building A from bottom of building B is 50 degrees. The angle of elevation of top of building B from bottom of Building A is 70 degrees. Find out which building is taller?(hint: no calculation needed, just common sense).

Answers

  1. 40
  2. 200
  3. 94.6
  4. 1) distance= 20 root 3 OR 34.6m 2) height of tree= 40 m 3) difference between heights= 20 m.
  5. 12m
  6. Building B is taller. (because second angle is 70 means from the bottom of building A, you’ve to raise you head even higher to see the top of building B.)

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