Sum

The banks of a river are parallel. A swimmer starts from a point on one of the banks and swims in a straight line inclined to the bank at 45º and reaches the opposite bank at a point 20 m from the point opposite to the starting point. Find the breadth of the river

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#### Solution

Let A be the starting point and B, the end point of the swimmer. Then AB = 20 m and ∠BAC = 45º.

`\text{Now, }\frac{BC}{AB}=\text{sin}45^\text{o}=\frac{1}{\sqrt{2}}`

`\Rightarrow \frac{BC}{20}=\frac{1}{\sqrt{2}}`

`\Rightarrow BC=\frac{20\times \sqrt{2}}{2}=14.14\m`

Concept: Heights and Distances

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