The proof is a little too long to type into my phone. But the answer is: 45 degrees above the horizon. Exactly halfway between straight out and straight up.
To maximize a projectile's range, it should be launched at an angle of 45 degrees. This angle balances the vertical and horizontal velocity components, allowing the projectile to achieve maximum distance. While real-world factors may alter this slightly, 45 degrees is the optimal angle in ideal conditions.
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