Last updated at May 29, 2018 by Teachoo

Transcript

Ex 9.1 , 11 A TV tower stands vertically on a bank of a canal. From a point on the other bank directly opposite the tower, the angle of elevation of the top of the tower is 60 . From another point 20 m away from this point on the line joining this point to the foot of the tower, the angle of elevation of the top of the tower is 30 (see figure). Find the height of the tower and the width of the canal. Let tower be AB So, height of tower = AB Given that,from a point on the other bank directly opposite the Tower,the angle of elevation of the tower is 60 . Hence, ACB = 30 Also, Angle of elevation from point D to top of the tower = 30 So, ADB = 30 Also, DC = 20 m We need to find height of tower AB & width of canal BC Since tower is vertical to ground So, ABD = 90 From (1) & (2) 3BC = / 3 3 3BC = BD 3BC = BD 3BC = BC + CD 3BC = BC + 20 3BC BC = 20 2BC = 20 BC = 20/2 BC = 10 m Hence, the width of the canal is 10 m From (1) AB = 3BC AB = 3 10 AB = 10 3 m Hence, height of tower = 10 3 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, 1

EX 9.1, 3

EX 9.1, 2

EX 9.1, 5

Ex 9.1, 7

Example 2

Example 3

Example 4

EX 9.1, 8

Example 5

Ex 9.1, 6

EX 9.1, 9

Ex 9.1, 10

Ex 9.1, 11 You are here

Example 6 Important

Ex 9.1, 12

Ex 9.1, 13 Important

Ex 9.1, 16

Example 7

Ex 9.1, 14 Important

Ex 9.1, 15 Important

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.