# Building 67654

The 15 m high building is 30 m away from the river bank. The river's width can be seen from the roof of this building at an angle of 15 °. How wide is the river?

### Correct answer:

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

**algebra**- expression of a variable from the formula
**planimetrics**- right triangle
- triangle
**goniometry and trigonometry**- sine
- cosine
- tangent
- arctangent

#### Units of physical quantities:

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