SOLUTION: On one side of a path walk is a pedestal with a flag staff on top of it. The pedestal 2m in height while the flag staff is 3m high. At the opposite edge of the path walk the pedest

Algebra ->  Trigonometry-basics -> SOLUTION: On one side of a path walk is a pedestal with a flag staff on top of it. The pedestal 2m in height while the flag staff is 3m high. At the opposite edge of the path walk the pedest      Log On


   



Question 1187815: On one side of a path walk is a pedestal with a flag staff on top of it. The pedestal 2m in height while the flag staff is 3m high. At the opposite edge of the path walk the pedestal flag staff subtend
s equal angles. Compute the width of the path walk

Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
The way I read the problem, it looks like this:
As seen across the walk path from an ant on the grass at the edge of the path opposite the pedestal,
the pedestal subtends an angle red%28A%29 , and so does the flag staff.
With the path walk surface being horizontal, and the pedestal and flag staff being vertical,
I see two right triangles, sharing the path width as one leg.
The height of the pedestal, 2m , is the other leg of one of those triangles, opposite angle A .
The sum of the heights of pedestal and flag staff, 2m%2B3m=5m , is a leg of the other triangle, opposite angle 2A%29 .
If x path width in m, from those right triangles, we get the trigonometric ratios:
tan%28A%29=2%2Fx and tan%282A%29=5%2Fx
Substituting those tangents into the trigonometric identity tan%282a%29=2%2Atan%28A%29%2F%281-tan%5E2%28A%29%29 , we get
5%2Fx%22=%222%282%2Fx%29%2F%281-%282%2Fx%29%5E2%29 --> 5%2Fx%22=%22%284%2Fx%29%2F%281-4%2Fx%5E2%29
Multiplying both sides times x%3C%3E0 , we get and equivalent equation:
5%22=%22%284%29%2F%281-4%2Fx%5E2%29
Assuming that x%3C%3E2 so that 1-4%2Fx%5E2%3C%3E0 , we multiply both sides times 1-4%2Fx%5E2 to get the equivalent equation
5%281-4%2Fx%5E2%29%22=%224 --> 5-20%2Fx%5E2=4 --> 5-4=20%2Fx%5E2 --> 1=20%2Fx%5E2 --> x%5E2=20 --> x=sqrt%2820%29 --> x=about+4.47
The path is highlight%284.47m%29 wide.