# River

From the observatory 11 m high and 24 m from the riverbank, river width appears in the visual angle φ = 13°. Calculate the width of the river.

### Correct answer:

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#### You need to know the following knowledge to solve this word math problem:

**algebra**- equation
**planimetrics**- Pythagorean theorem
- right triangle
- triangle
- The Law of Sines
**basic functions**- reason
**goniometry and trigonometry**- tangent
- arctangent

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