`A,B,C, and D` are four trees, located at the vertices of a square (Fig. 5.117). Wind blows from `A to B` with uniform speed. The ratio of times of flight of a bird from `A to B` and from `B to A` is `n`. At what angle should the bird fly from the direction of wind flow, in order that it starts from `A` and
(a) reaches `C`,
(b) reaches `D` ?

Explanation

To solve the problem of determining the angle at which a bird should fly from tree A to reach trees C and D, we will follow these steps:

### Step 1: Understand the Problem
We have four trees located at the vertices of a square: A, B, C, and D. The wind blows uniformly from A to B. The bird's flight time from A to B and from B to A is given in a ratio of \( n \). We need to find the angles for the bird to reach C and D.

### Step 2: Define Variables
- Let \( u \) be the speed of the wind.
- Let \( v \) be the speed of the bird.
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