Given the angle of deviation as seen by the pilot is equal to 15 degrees,
i.e the angle made by the line of sight with the ground is 15 degrees also the angle of elevation from a person at ground to the otherplane is given to be equal to 15 degrees
which means the angle made by line of sight to plane and ground is equal to 15 degrees hence both of these situations refer to the sameangle at a point and hence bothplanes are descending at the sameangle.
A two story home might use translation to have both floors identical and most homes have windows of the same size and shape so they might also use translation. Sometimes buildings use reflection to make rooms opposite each other the same.
