Final answer:
The angle at which a projectile's range is zero is at either 90° or 0°, since these angles correspond to a vertical launch and a horizontal point, respectively. For maximum range, the ideal launch angle is 45°, and for a vector to have a greater x-component than y-component, its angle should be less than 45°.
Step-by-step explanation:
The angle at which a projectile's range is equal to zero is at 90° or 0°. This is because at 90°, the projectile is launched straight up, and at 0°, it is launched horizontally with no vertical component to its velocity, thereby having no range as it would just be a point on the ground. For optimum range, the angle should be 45°. If a vector's x-component is to be greater than its y-component, the vector's angle with respect to the positive x-axis should be between 0° and < 45°.