Question

What is boost parameters and hyperbolic trognometry in relativity ?

Answer 1

Boost parameter is

$$\theta=tanh^{-1}(\frac{v}{c})$$

Boost parameters are part of the native Minkowskian geometry of spacetime, they allow us to see the rule for combining boosts in a simple form. [Marolf D. Notes on Relativity and Cosmology (2003)]