This is homework so dont give a complete answer. I just Dont understand what my professor means by the question:
"Determine the images under the stereographic projection of all the lines l[-3,9,a], a is a real parameter. Give the equation as a second degree equation in two variables"
Lines in C go to circles on S through the north pole N(0,0,1). First thought she meant describing the circles. So x^2+y^2=r^2 and the problem part was finding the radius. But asked her and she started talking about how if you stand in the origin it looks like an ellips. But if a=0 and you stand in origo what? What plane am i suppose to project the circle onto to get an ellips?
Can someone Pleeease explain what she means/idea of how to go about solving it? Just have no idea what to do :(