calculation of x & y using radii from 2 points of known x & y

Hi,

I have a forestry square plot of 30m, with sides called A, B, C, & D. I know the co-ordinates for both ends of side A. For every tree within the plot, I have a measurement for the distance to both ends of side A. I wish to know the co-ordinates of every tree.

Is there a way for ArcGIS to calculate this? I don't have Spatial Analyst, though do have the ET add-ins.

Regards, Mick.