You have 0 cows because it didn’t tell how many cows there were
The transformation (x,y) --> (x,-y) is reflection over x axis. while the x coordinates in the image stay the same as the original, y coordinates change the sign.
Therefore coordinates of original image and final image after reflection
E - (0,3) --> E' (0,-3)
F - (2,2) --> F' (2,-2)
G - (1,1) --> G' (1,-1)
The diagram attached shows both the original image and image after reflection
Short answer: - 1
The first thing you should do is draw this or get a program to do it. I use desmos. It is included. The graph shows one complete cycle every 2*pi intervals (or 360 degrees.)
You will find no lower value that y = - 1 (nor any value greater than y = 1)