A particle of mass `m` has been thrown with intial speed `u` making angle `theta` with the horizontal ground. Find the angular momentum of the projectile about an axis perpendicular to the plane and passing through the point of projection when the projectile is
`(a)` At the highest point
`(b)` About to hit the ground

Explanation

To find the angular momentum of a projectile about an axis perpendicular to the plane and passing through the point of projection, we will analyze two scenarios: (a) when the projectile is at its highest point and (b) when it is about to hit the ground.

### Given:
- Mass of the particle = \( m \)
- Initial speed = \( u \)
- Angle of projection = \( \theta \)

### (a) Angular Momentum at the Highest Point
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