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A tower subtends angles alpha,2alpha,3al...

A tower subtends angles `alpha,2alpha,3alpha` respectively, at point `A , B ,a n dC` all lying on a horizontal line through the foot of the tower. Prove that `(A B)/(B C)=1+2cos2alphadot`

A

`(sin 3alpha )/(sin2alpha)`

B

`1+2 cos 2 alpha`

C

`2 cos 3 alpha`

D

`(sin 2 alpha )/(sin alpha ) `

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B
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OBJECTIVE RD SHARMA ENGLISH-HEIGHTS AND DISTANCES-Exercise
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  2. A ladder rests against a vertical wall at angle alpha to the horizonta...

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  3. From the top of a cliff 300 metres high, the top of a tower was obser...

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  4. The angles of elevation of the top of a tower at the top and the foot ...

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  5. A person standing on the bank of a river finds that the angle of elev...

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  6. A tower subtends an angle of 30^@ at a point on the same level as the ...

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  7. AB is a vertical pole. The end A is on the level ground .C is the midd...

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  8. The angle of depression of a point situated at a distance of 70 metres...

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  9. The angle of elevation of the top of a vertical tower from two points ...

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  10. An aeroplane flying horizontally 1 km above the ground is observed ...

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  11. about to only mathematics

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  12. At a distance 12 metres from the foot A of a tower AB of height 5 met...

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  13. A tower 50 m high , stands on top of a mount, from a point on the grou...

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  14. A person on a ship sailing north sees two lighthouses which are 6 km a...

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  15. An observer finds that the elevation of the top of a tower is 22.5^@ a...

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  16. A vertical lamp-post, 6m high, stands at a distance of 2 m from a wall...

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  17. The angle of elevation of the top of a vertical pole when observed ...

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  18. The upper 3/4 th portion of a vertical pole subtends an angle theta su...

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  19. A person standing on the bank of a river observes that the angle of ...

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  20. A tower subtends angles alpha,2alpha,3alpha respectively, at point A ,...

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