The angle of elevation from a point P of the top of a tower QR, 5

The horizontal distance between two towers is 120 m. The angle of elevation of the top and angle of depression of the bottom of the first tower as observed from the second tower is and 24°respectively.

Find the height of the two towers. Give your answer correct to 3 significant figures.


Consider the following figure:

In AEC,

tan30° = AEEC

 13 = AE120

 AE = 69.28m

In BEC,

tan24° =EBEC

 0.445 = EB120

 EB = 53.427m

Thus, the height of first tower, AB = AE + EB

                                                  = 69.282 + 53.427

                                                  = 122.709m = 122 m

And height of second tower, CD = EB = 53.427m = 53.4m


An aeroplane at an altitude of 250 m observes the angle of depression of two boats on the opposite banks of a river to be 45° and 60° respectively. Find the width of the river. Write the answer correct to the nearest whole number.


Let consider A be the position of the aeroplane and let BC be the river. Let D be the point in BC just below the aeroplane.

For ΔADC, we get

tan45° = hy

 1 = 250y

 y = 250m

For ΔADB, we get

tan60° = ADDB

 3 = hx

 3 = 250x

 x = 2503m

Therefore, the width of the river is DB + DC = 250 + 2503 = 394m.


The angles of depression of two ships A and B as observed from the top of a light house  60 m high are  600  and  45 respectively. If the two ships are on the opposite sides of the light house, find the distance between the two ships, Give your answer correct to the nearest whole number.


                      

Let  PQ  be the light house.

 PQ= 60In  PQA,tan 60° = PQAQ 3 = 60AQ AQ = 603 AQ = 20 X 33 AQ = 20 X 3 X 33 AQ = 20 3 m.

 

In PQB,tan 45° = PQQB  1 = 60QB QB = 60 mNow,AB = AQ + QB      = 20 3 + 60

      = 20  x  1.732  +  60 

      = 94.64

      = 95 m.


An aeroplane at an altitude of 1500 metres, finds that two ships are sailing towards it in the same direction. The angles of depression as observed from the aeroplane are  450  and  300 respectively. Find the distance between the two ships.


                        

A   is the aeroplane, D  and  C  are the ships sailing towords  A.

Ships are sailing towords the aeroplane in the same direction.

in the figure, height  Ab = 1500 m.

To find:  Distance between the ships, that is  CD.

Solution: 

In the right-angled ABC,tan 45° = ABBC 1 = 1500BC BC = 1500 m.In the right-angled  ABD,tan 30° = ABBD  13 = 1500BD BD = 1500 3 BD = 1500 ( 1.732 )            = 2598 m Distance between the ships = CD = BD - BC                                                 = 2598 - 1500                                                 = 1098 m.


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The angle of elevation from a point P of the top of a tower QR, 50 m high is 600 and that of the tower PT from a point Q is 30°. Find the height of the tower PT, correct to the nearest metre.

                       


In  PQRtan 60° = RQPQ3 = 50PQPQ= 503In  PQTtan 30° = PTPQ13 = PT503PT = 13 × 503PT = 503.


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