Flight path angle should not be
confused with pitch angle. Pitch angle is the angle between a line drawn
through the aircrafts nose and the horizontal. Flight path angle is the angle
between the the aircrafts velocity vector and the
horizontal.
Descending at a constant mach
increases the IAS which means the descent angle will increase but we will be
reducing angle of attack to keep the lift formula in balance, so pitch angle
will decrease.
Now terminology and interpretation
become a factor in answering the question. You could describe a bigger nose
down pitch as either increasing the (negative) pitch angle or decreasing the
(positive) pitch angle. The examiners’ view is that, if you move from a cruise
pitch of 2-3º up to a descent pitch of 2-3º down, you have decreased your pitch
angle.