
\magnification=\magstep2


$$
{\rm avg\ intensity\ within\ R}\quad {I_a}(R) \quad = 
      \quad
        {{\int_{0}^{R} { I(r) 2 \pi r dr}} \over {\pi R^2}}
$$

$$
{\rm at\ the\ Petrosian\ radius\ }R_P \quad \quad 
      I(R_P) \quad = \quad 
            \eta \  \left(   { {\int_{0}^{R_P} { I(r) 2 \pi r dr}} \over {\pi R_P^2}} \right)
$$

$$
F_P \quad = \quad \int_0^{kR_P} I(r) 2 \pi r dr 
$$


$$
C \quad = \quad {{r_{90}} \over {r_{50}} }
$$


\bye
