A projectile is fired with a speed u at an angle `theta` with the horizontal. Find its speed when its direction of motion makes an angle `alpha` with the horizontal.

Explanation

To find the speed of a projectile when its direction of motion makes an angle \( \alpha \) with the horizontal, we can follow these steps:

### Step 1: Understand the Components of Velocity
When a projectile is fired with an initial speed \( u \) at an angle \( \theta \), its initial velocity can be broken down into horizontal and vertical components:
- Horizontal component: \( u_x = u \cos \theta \)
- Vertical component: \( u_y = u \sin \theta \)

### Step 2: Analyze the Horizontal Motion
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