Posted by Amy on .
Given any Cartesian coordinates, (x,y), there are polar coordinates (r,theta) with –pi/2< theta < pi/2.
Find polar coordinates with –pi/2 < theta < pi/2 for the following Cartesian coordinate:
If (x,y) = (11,–7) then (r, theta)=( ____, _____ )
I was able to find r using r^2=x^2 + y^2, but I can't find theta. I found r to be 170^(1/2). I then tried using x= r*cos(theta), plugged in x=11 and r= 170^(1/2) and got theta = inverse cos (11/170^(1/2)), but that's not the correct answer. However my answer for r is correct. Any help would be very much appreciated, and thank you in advance! a detailed explanation would be nice since I still have several problems similar to this one to do :)

Math (Calculus) 
Amy,
nvm i got it