prove that:
first, the coordinates of
and the coordinates of
and
so thot from these that using I could get the coordinates of
but did not unless I made an error somewhere....
Hmm, the way I'm coming up with is pretty long.
Looking at the unit circle, you can define point P at and Q at . O is the origin. Then find the line perpendicular to line OQ going through P, call it line m. Find the intersection of m and OQ, call it point Z. Then verify that the length of line segement PZ divided by the length of line segment OZ is 2/3.
Someone care to share a better way?