Answers

2014-11-15T12:39:13+08:00
It's trigonometry

after making some sketch you should know that

tan20° = 50/x

where x is the angle of elevation

Multiply both by x

x(tan20°) = (50/x)x

xtan20° = 50

divide both by tan20°

xtan20°/tan20° = 50/tan20°

x = 50/tan20°

Now using a calculator we may divide 50 to the value of tan20°

x = ~149

I hope it helps


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