1. The problem statement, all variables and given/known data Eliminate the parameter to find a description of the following circles or circular arc's in terms of x and y and find the center and radius and indicate the positive orientation x=cos(t) , y = 3sin(t) ; 0< t < pi/2 (should be less than or equal to) 2. Relevant equations Not sure? 3. The attempt at a solution When I find t = arccos(x) I then plug it in y=3 sin(t) and I result in y= sqrt(9-x^2) The book doesn't even give an answer for the equation part but it does tell me the origin, and radius and the orientation but I figured you could rewrite my equation to y^2 + x^2 = 9 and that tell me the radius of 3 (sqrt (9) right?) then the orgin is 0,0 because nothing it being done to the x and y but here is what trips me up, how do they know it is the lower half of a circle going counter clockwise? I mean it has to do something with the t's but I just dont see it.