1.

Two poles stand at either side of the roadHeight of the poles are in the ratio 1:2The road is 90 feet wideThe angle of elevation of both the poles from a point in between the road is 60degree find the height of the poles

Answer»

Let \: AB \:and \:CD \:are \:two \:poles .

AB : CD = <klux>1</klux> : <klux>2</klux> \: ( given )

Let \: AB = x \:ft , \: CD = 2x \:ft

Distance \: between \:two \:poles (BD) = 90 \:ft

Let \: BO = y \:ft , \\and \: OD = (90 - y) \:ft

In \: \triangle AOB , we \:have ,\\tan \: \angle {AOB} = \frac{AB}{BO}

\implies tan 60 \degree = \frac{x}{y}

\implies \sqrt{3} = \frac{x}{y}

\implies y = \frac{x}{\sqrt{3}} \: ---(1)

In \: \triangle COD , we \:have ,\\tan \: \angle {COD} = \frac{CD}{OD}

\implies tan 60 \degree = \frac{2x}{(90-y)}

\implies \sqrt{3} = \frac{2x}{(90-y)}

\implies 90 - y  = \frac{2x}{\sqrt{3}}

\implies y = 90 - \frac{2x}{\sqrt{3}}\: ---(2)

/* From (1) and (2) */

\frac{x}{\sqrt{3}} = 90 - \frac{2x}{\sqrt{3}}

\implies \frac{x}{\sqrt{3}} + \frac{2x}{\sqrt{3}} = 90

\implies \frac{3x}{\sqrt{3}} =90

\implies x = 90 \times \frac{\sqrt{3}}{3} \\= 30\sqrt{3}

Now, Height \:of \:the \:pole (AB) = 30\sqrt{3} \:ft

Now, Height \:of \:the \:pole (CD) \\= 2x\\=  2 \times 30\sqrt{3} \\= 60\sqrt{3} \:ft

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