\magnification=\magstep2

$$
\lambda_{\rm obs} \quad = \quad \lambda_{\rm source} \thinspace
                      {{ \sqrt{1 + \beta} } \over { \sqrt{1 - \beta }} }
   \quad \quad = \quad \quad  
                                \lambda_{\rm source} \thinspace
                      {{ \sqrt{1 + (v/c)} } \over { \sqrt{1 - (v/c) }} }
$$

$$
\lambda_{\rm obs} \quad \simeq \quad \lambda_{\rm source} \thinspace
                      {({ 1 + \beta })}
          \quad \quad = \quad \quad 
                      \lambda_{\rm source} \thinspace {({ 1 + (v/c) })}
$$

$$
{\rm velocity \ (km/s)} \quad = \quad H \thinspace\thinspace\thinspace {\rm distance\ (Mpc)}
$$

$$
z \quad = \quad {{ \lambda_{\rm obs}} \over {{\lambda_{\rm source}} } }  \thinspace - 1
$$


$$
\beta \quad \equiv \quad {{v}\over{c}}
$$


\bye
