If a rapidly rotating gyroscope attached to a perch is released in a horizontal position -- that is, so that the axis of the gyroscope is horizontal -- the gyroscope will precess around it's perch. Let L represent its angular momentum. Let dL represent a small change in that momentum. Let dA represent the corresponding change in the angle of L. According to all the references I've found, dA = dL/L. I don't understand this. Shouldn't dL/L be the change in the sine of the angle, not the angle? See attached diagram. Thanks.