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A telegraph post is bent at a point above the ground due to starm. Its top just touches the ground at a distance of 10 √3 metre from its foot and makes an angle of 30° with the horizontal. Then height (in metres) of the telegraph post is
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- 30
- 24
- 20
- 25
Correct Option: A
AB = Telegraph post
AC = CD = bent part
BD = 10√3 metre
In ∆BCD,
| tan 30° = | |
| BD |
| ⇒ | ⇒ | ||
| √3 | 10√3 |
| ⇒ BC = | × 10√3 | |
| √3 |
= 10 metre
Again,
| sin 30° = | |
| CD |
| ⇒ | = | ||
| 2 | CD |
⇒ CD = 20 metre
∴ AB = BC + CD = (10 + 20) metre
= 30 metre
