Question 1192810
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Sara and Junya made a string telephone and tested if it works. 
Sara stood at the top of a tower while Junya stayed at the ground level. 
From Sara’s viewpoint, the angle of depression of Junya is 64° with the horizontal. 
Junya is 10.5 m from the base of the tower. How long is the string of their improvised telephone?
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            The solution by @josgaritmetic is  FATALLY  WRONG  and  CONCEPTUALLY  INCORRECT.


            I came to bring you a correct solution.



<pre>
Make a sketch.


Let x be the length of the string, in meters (the value under the problem's question).


Your sketch represents right angled triangle with the hypotenuse of x meters long.


Horizontal leg is 10.5 meters, and the angle beteen this leg and the hypotenuse 
(the adjacent leg) is 64°.


So you write

    x*cos(64°) = 10.5.


From this equation find x

    x = {{{10.5/cos(64^o)}}} = {{{10.5/0.438371}}} = 23.95231436 meters.


We round this value to 2 decimal places to a bit greater value and get the answer  23.96 meters.


<U>ANSWER</U>.  The length of the string is 23.96 meters, approximately.
</pre>

Solved.


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For the safety of your mind, ignore the post by josgarithmetic.


Keep in mind that 80% or 90% of his "solutions" at this forum are incorrect.



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After seeing my post, @josgarithmetic tried to make corrections in his post,


but his updated post is still incorrect, since he uses INCORRECT angle of 26 degrees instead of correct 

depression = elevation angle of 64 degrees.



This person simply does not know elementary Math and is absolutely careless about his writing (is not able to write correctly).