The total length L of an open belt drive is given by L = 2C + π(D1 + D2)/2 + (D1 − D2)2 / (4C), where C is the centre distance and D1, D2 are the pulley diameters. What does the term (D1 − D2)2 / (4C) represent?

For transmitting power, a simple gear train consisting of an odd number of gears (9 gears) is used. The driver shaft and driven shaft will rotate in:

For maintaining a constant velocity ratio and positive drive over a relatively large distance between driving and driven shafts, one should use a: