How tall is that telephone pole????

S

shelarson

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The sun is at 70 degree from the horizon. The telephone pole downward 10 degree slope. The shadow of the telephone pole is 65 feet. How tall is the telephone pole? How would you set up this problem?
 
shelarson said:
The telephone pole downward 10 degree slope. I'm not sure what this sentence means.
Click to expand...

Are you trying to find the value of x, in the image below?

(Double-click the image, to expand it. Also, I forgot to indicate that the vertical dashed line is perpendicular to the triangles' base. In other words, the larger triangle is a right-triangle.)

[attachment=0:nvwex0yn]Pole.JPG[/attachment:nvwex0yn]
 

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You may need to clarify what you mean by "downward 10 degree slope." Is the pole perpendicular to the ground which is on a 10 degree slope or is the pole leaning 10 degrees on a 10 degree slope? In other words, is the pole pointing towards the center of the earth on a 10 degree incline?

Either way, the sun's ray will make a triangle with the legs being the pole, the shadow and the sun's ray from the tip of the pole to the tip of the shadow. Then you know the length of the shadow and the angle between the pole and the ground (either 90 or 100 depending on the above question) If it's 90 degrees, it's a simple computation from a 30 60 90 triangle. Let me know if this helps, otherwise I need the clarification above.
 
Tutor Joel is correct. The shadow and the pole are two legs of a 30-60-90 triangle. (I had to draw a picture, to discover that. The picture also shows that the side representing the pole is opposite a known angle whose adjacent side is also known.)

Do you know how to use the tangent function, to find the height of the pole?

If you need more help, please explain why you're stuck.

If you feel like you don't really understand anything about right triangles and trig functions, then let me know. (In right-triangle trigonometry, the trig functions for acute angles are all defined as ratios of sides of right triangles). I will look for some basic lessons on-line, for you.

Cheers ~ Mark 8-)
 
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