In your "distance formula", you're square-rooting when you should square.
2. From a lighthouse, the range of visibility on a clear day is 40 km.
On a coordinate system, where O(0,0) represents the lighthouse,
a ship is travelling on a course represented by: .
Between which two points on the course can the ship be seen from the lighthouse?
Q * |
* * |
P * * |
o * |
* * * |
- - - - - - - - - - - * - - - -
and have coordinates such that: .
We want: .
So we have: .
The ship can be seen from to