Spherical (or polar) ctr-ordinates A. t--- I I 4 Here a point in space is referenced by In Its distance. r. from the origin a The angle. gin. that the line connecting the point to the origin makes with its projection onto a xed plane through the origin ' The angle. 9. that the projection line on the xed plane makes with another fixed line in the plane through the origin We can now reference the point by f r, 3. {ll} Treating the earth as a perfect sphere and looking at points on the surface of the earth. what does 6 refer to? Similarly what does refer to? What are the coordinates in a rectangular Cartesian frame of reference? Where is the point {0. 0, 0)? Is there a point (-r, 9. qt)? What is the point (r. 9. lit/2) co the earth's surface