Translations:Sketcher ConstrainSnellsLaw/9/en

where:
 * Sketch is a sketch object
 * line1 and pointpos1 are two integers identifying the endpoint of the line in medium with refractive index of n1. line1 is the line's index in the sketch (the value, returned by Sketch.addGeometry), and pointpos1 should be 1 for start point and 2 for end point.
 * line2 and pointpos2 are the indexes specifying the endpoint of the second line (in medium n2)
 * n2byn1 is a floating-point number equal to the ratio of refractive indices n2/n1