River
From the observatory 18 m high and 31 m from the riverbank, river width appears in the visual angle φ = 20°. Calculate the width of the river.
Correct answer:

Tips for related online calculators
Do you have a linear equation or system of equations and are looking for its solution? Or do you have a quadratic equation?
Do you want to convert length units?
See also our right triangle calculator.
See also our trigonometric triangle calculator.
Try conversion angle units angle degrees, minutes, seconds, radians, grads.
Do you want to convert length units?
See also our right triangle calculator.
See also our trigonometric triangle calculator.
Try conversion angle units angle degrees, minutes, seconds, radians, grads.
You need to know the following knowledge to solve this word math problem:
algebraplanimetricsbasic operations and conceptsgoniometry and trigonometryUnits of physical quantitiesGrade of the word problem
Related math problems and questions:
- View angle
From a tower 20 m high and 20 m away from the river, the width of the river appears to be at an angle of 15°. How wide is the river at this location?
- Calculate 5148
At a distance of 10 m from the river bank, they measured the base AB = 50 m parallel to the bank. Point C on the other bank of the river is visible from point A at an angle of 32°30' and from point B at an angle of 42°15'. Calculate the width of the river
- Big tower
From a tower 15 meters high and 30 meters away from the river, the width of the river appeared at an angle of 15°. How wide is the river in this place?
- Bridge across the river
The width of the river is 89 m. For terrain reasons, the bridge deviates from a common perpendicular to both banks by an angle of 12° 30 '. Calculate how many meters the bridge is longer than the river.
- 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?
- The swimmer
The swimmer swims at a constant speed of 0.85 m/s relative to water flow. The current speed in the river is 0.40 m/s, and the river width is 90 m. a) What is the resulting speed of the swimmer for the tree on the riverbank when the swimmer's motion is per
- Tree
How tall is the tree observed at the visual angle 45°? If I stand 3 m from the tree, my eyes are two meters above the ground.