Launch at an Angle

Launched at $\relax v_0$ and an angle $\theta$, split the velocity into components:

$$v_{0x} = v_0 \cos\theta, \quad v_{0y} = v_0 \sin\theta$$

The horizontal part stays the same. The vertical part drops by $9.8\ \mathrm{m/s}$ every second and is zero at the top, where the ball still moves sideways.

At the top the vertical part is zero; the horizontal part is still vx.