I attached a free body diagram for a better understanding of this problem.
We start making summation of Moments in A,



Then we make a summation of Forces in Y,



At the end we calculate the angle with the sin.


Answer:
Answer: Sound waves and some earthquake waves are longitudinal waves. Ocean, light and other earthquake waves are transverse waves.
Explanation:
There are 2 types of waves:
1. Longitudinal waves: These waves are defined as the waves in which the particles of the medium move in the direction of the wave. This requires a medium to travel. For Example: Sound Waves.
2. Transverse wave: These waves are defined as the waves in which the particles of the medium travel perpendicularly to the direction of the wave. This does not require a medium to travel. These can travel in vacuum also. For Example: Light waves.
Hence, Sound waves and some earthquake waves are longitudinal waves. Ocean, light and other earthquake waves are transverse waves
Answer:
Xcm = (6 * 0 + 4 & 3 + 2 * 0) / 12 = 1
Ycm = (6 * 0 + 4 * 0 + 2 * 3) / 12 = 1/2
(Xcm , Ycm) = (1 , 1/2)
Using definition of center of mass