Last updated at May 29, 2018 by Teachoo

Transcript

Ex 9.1 , 7 From a point on the ground, the angles of elevation of the bottom and the top of a transmission tower fixed at the top of a 20 m high building are 45 and 60 respectively. Find the height of the tower. Let the building be AB and tower be CA. Building is 20 m high, So, AB = 20m Let point of ground be P. Angle of elevation from point P to bottom of tower A = 45 Hence, APB = 45 Also, Angle of elevation from point P to top of the tower C = 60 Hence, CPB = 60 We need to find AC. Since building is vertical, ABP = 90 . In right angle triangle APB, tan P = ( " " )/( " " ) tan P = / tan 45 = 20/ 1 = 20/ PB = 20 m Similarly, in right angle triangle CPB, tan P = ( " " )/( " " ) tan P= / tan 60 = / 3 = /20 20 3 = BC BC = 20 3 AB + AC = 20 3 20 + AC = 20 3 AC = 20 3 20 AC = 20 ( 3 1) m Hence, Height of tower = AC = 20 ( 3 1) m

Questions easy to difficult

Angle of Elevation and Angle of Depression

Angle of Depression from point A to point B is same as Angle of Elevation from point B to point A

How to find Height when angle of elevation is given?

How to find Distance when angle of depression is given?

Example 1

EX 9.1, 4

EX 9.1, 5

EX 9.1, 3 Important

EX 9.1, 2 Important

Ex 9.1, 7 You are here

Example 4

Example 2 Important

EX 9.1, 8

Example 5 Important

Ex 9.1, 11 Important

Example 7 Important

Example 3 Important

Ex 9.1, 6 Important

EX 9.1, 9 Important

Ex 9.1, 10 Important

Example 6 Important

Ex 9.1, 13 Important

Ex 9.1, 12 Important

Ex 9.1, 16 Important

Ex 9.1, 14 Important

Ex 9.1, 15 Important

EX 9.1, 1

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.