(a) Equation 12.40 defines proper velocity in terms of ordinary velocity. Invert that eq...

(a) Equation 12.40 defines proper velocity in terms of ordinary velocity. Invert that equation to get the formula for u in terms of η.

(b) What is the relation between proper velocity and rapidity (Eq. 12.34)? Assume the velocity is along the x direction, and find η as a function of θ.

Equation 12.34