A ball is projected from a given point with velocity u at some angle with the horizontal and after hitting a vertical wall returns to the same point. Show that the distance of the point from the wall must be less than `(eu^2)/((1+e)g)`, where e is the coefficient of restitution.

Explanation

To solve the problem, we will follow a systematic approach to derive the required expression for the distance from the wall.

### Step-by-Step Solution:

1. **Understanding the Problem**:
A ball is projected with an initial velocity \( u \) at an angle \( \theta \) with the horizontal. After hitting a vertical wall, it returns to the same point. We need to show that the distance \( D \) from the point of projection to the wall must be less than \( \frac{eu^2}{(1+e)g} \), where \( e \) is the coefficient of restitution.

2. **Break Down the Initial Velocity**:
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