Answer
See work.
Work Step by Step
If the projectile is thrown straight up, all of its initial kinetic energy is transformed into gravitational potential energy, and it reaches a maximum height.
If it is thrown at some angle away from the vertical at the same speed, when it reaches its maximum height it still possesses kinetic energy (due to its horizontal component of velocity), so its PE is less. This means that it doesn’t rise to the same maximum height.
