Q.trignometry question (1 Viewer)

[freaking_out]

i think this question does not have enough information:


David walks along a straight road. At one point he notices a tower on a bearing of 53 degrees with an angle of elevation of 21 degrees.
After walking 230m, the tower is on a bearing of 342 degrees, with an angle of elevation of 26 degrees. Find the height of the tower correct to the nearest metre.

thanx in advanced,

 

[maniacguy]

There is in fact enough information:

Let A be the initial point where he decided to look at the tower
Let B be the second point where he looks at the tower
Let T be the foot of the tower.
Let h be the height of the tower.

Then h/AT = tan 21, h/BT = tan 26 (all angles in degrees)

Thus AT = h*cot(21), BT = h*cot(26), AB = 230

Further, using the bearings of 53 degrees and 342 degrees, it is possible to determine the angle ATB as 53 + 18 = 71 degrees

(construct lines from north to south running through each of A, T, B - these are parallel, and alternate angles can be used).

Now use the cosine rule to determine h^2 and so h.

 

[freaking_out]

Now use the cosine rule to determine h^2 and so h.

i know this might sound dumb... can you pls. elaborate on which triangle to use the cosine rule on ???