posted by Greg .
he distance between 2 points (x1,Y1) and (x2,y2) is given by d = square root (x1-x2)^2 + (y1-y2)^2
a - pick 2 arbitrary points in 3 dimensions, (x1, y1, and Z1) and (x2,y2,z2) and plot these points. Not that there are 90 degrees between the xy, xz, and yz axes.
b- using your sketch from part a, find the distance between these 2 points, generalize the above equation to 3 dimension