Add a formal equation to the report.

## Usage

addEquation( equation, ref = None )

## Parameters

equation (string)
The desired equation in LaTex format.
ref (string)
Label of the equation for further reference.

None

## Description

This routine adds a formal equation to the report. The equation is given by equation. The ref argument is the label of the equation for further reference. For example,
rep.addEquation( r'\rho u_{i,t} + \rho u_j u_{i,j} = -p_{,i} + \tau_{ij,j} + \rho b_i', ref = 'eqn:continuity' )