Question 217649
Radius  of  the  Earth  is  approx  3960  mi
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If  a  tower   is  15  ft  above  this,  the  distance  is  15 ft /5280 ft/mi = .00284  mi,,,,,and  the  distance  to  the  ctr  of  Earth  is  3960 + .00284 mi
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If  we  construct  a  right triangle, one  vertex  at  the  top  of  the  tower,
one  at  the  center  of  the  Earth,  and  another at  the  horizon point  from  the  tower,,,,we  find  a  right  triangle, one  leg 3960 mi, the  hypotenuse = 3960.00284 mi,  and  the  other  leg  the  distance  to  the  horizon. ( this  leg  is  tan  to  curvature  of  Earth,,hence  90 degree  angle)
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using  the Pythagorean  Theorem ,,c^2 = a^2 +b^2,
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(3960,00284)^2 = d^2 + 39606^2
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d= 4.7434 miles,,,,,,distance  to  horizon from  tower.
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