Angle of Projection for Maximal Height
The angle of projection for a projectile at its maximum height can be determined using the fact that the speed of the projectile at its maximum height is half of its initial speed.

Explanation
- When a projectile is launched at an angle, it follows a parabolic path. At the maximum height of the projectile, the vertical component of its velocity is zero.
- The vertical component of the initial velocity can be calculated using the formula v_y = v_i * sin(theta), where v_y is the vertical component of velocity, v_i is the initial velocity, and theta is the angle of projection.
- At the maximum height, v_y = 0. Therefore, v_i * sin(theta) = 0.
- This implies that either v_i = 0 or sin(theta) = 0. Since the initial velocity cannot be zero, sin(theta) must be zero.
- The value of sin(theta) is zero when theta = 0 or theta = 180 degrees. Therefore, the angle of projection for maximal height can be either 0 degrees or 180 degrees.
In conclusion, the angle of projection for a projectile at its maximum height is either 0 degrees or 180 degrees, depending on the direction of projection.