Question 209816
A  rough  sketch  might  help
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It  is  a  right  triangle,  with  hypotenuse = 15,  and  one  angle  =70 deg
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Let  the  distance  to  the  wall  be  x
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the  trig  function  is  adjacent / hyp or cos
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therefore,,,,cos 70 = x/15,,,or  x=15 cos 70 = 5.13
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check. cos  70 = 5.13 / 15 = .3420,,,,ok
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