Polar Coordinates: Traveling Clockwise from (0,-1) to (0,1)

[phamdat1202]

Homework Statement

the circle travels clockwise from (0,-1) to (0,1)
write down the parameterization in term of t

Homework Equations

The Attempt at a Solution

x=cost(t)
y=-sin(t)

i'm not sure about the sign of the polar coordinate, how to find the sign?

 

[zhermes]

Think about the extremes, what should the values be at t = 0? what about t = pi?