This document discusses the metric tensor, which describes how distances are measured in different coordinate systems. It gives the general formula for the metric tensor gij in terms of partial derivatives of the coordinate transformations. As an example, it derives the specific form of the metric tensor in spherical polar coordinates, obtaining the known result that the line element ds2 is given by (dr)2 + r2(dฮธ)2 + r2sin2ฮธ(dฯ)2.