Question

How are the coordinates of the new point found if it is rotated 180° counterclockwise? How many degrees is that equivalent to if the rotation is clockwise?

Answer 1

Remember 180 is a straight line

Answer 2

Here θ = 180 deg; cos(180) = -1 and sin(180) = 0
So, (x₁,y₁) = (x*-1-y*0, x*0+y*-1) = (-x,-y)

Answer 3

http://www.mathwarehouse.com/transformations/rotations-in-math.php
this website shows the turn pretty cool