problems with r.mapcalc

[John Stamm]

Hello.  I have used r.slope.aspect to generate a raster map of 
slopes.  The map has labeled each point with slope in degrees.
I would like to get slope as the tangent of the degrees.  I used
r.mapcalc, and used the equation:

tan.0 = tan(@slope.0)

where tan.0 is my output map and slope.0 is the raster map with
slopes.  However, I get tangent values equal to either zero or
one, and no fractional values.  Can anyone help?

John Stamm