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If we know the three principal strains and the angle between the plane or line in the XZ and YZ(or XY)planes, say f1 and f2, then it is possible to find the orientation of this line in the undeformed state assuming that lines and planes behave as passive markers during the deformation(see e.g. Ramsay, 1967). Ramsay has also plotted the graphical relationship between the ratios Z/X, Y/X and Z/Y and the respective angles phi1, f2 and f3 in deformed state & the equivalent angles f1, f2 and f3 in the undeformed state. This is given by:                                                                                                                                        
f'1=tan-1[(Z/X)tan f1]   
 f'2=tan-1 [(Z/Y)tan f2]   and     
 f'3=tan-1 [(Y/X)tan f3]        

                                                                                                                                                                    You are asked to input the values of X or 1+e1, Y or 1+e2 and Z or 1+e3. Also enter any two angles, i.e. phi1 in XZ plane and phi2 in XY plane. These angles must be from X in XZ and from X in XY plane. You will get new angles phi'1 and phi'2 plotted on the graph of 1/R against phi and also the values of these angles will be given at the bottom of the graph. You may replot your plane or line on the basis of these newer angles on the Schmidt net depending on where exactly your X, Y and Z lie on this. In the original Cloos program, the original plane is plotted with principal plane orientations input by user. A simple calculation program was developed in 1993 by the author in GWBASIC with input by values on a screen and the values returned as numerical answers on a DOS screen. It formed a package for strain determination and was dedicated to E Cloos, and also christened CLOOS. This particular one formed a part of a long file called Nadai.bas.