Question

how do you change from cartesian coordinates to polar coordinates when you x=0, because you cant use tan=y/x

Answer 1

well cordinate means (x,y) we need both to convert

Answer 2

tan(pi/2)= sin(pi/2)/cos(pi/2)=1/0=infinity so not a probe
tan theta =y/x=y/0=infinity means theta = pi/2

Answer 3

but for r u need to be known y value